vcodecs.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright 2007-2008, Sergio Fadda, Luigi Rizzo
 *
 * See http://www.asterisk.org for more information about
 * the Asterisk project. Please do not directly contact
 * any of the maintainers of this project for assistance;
 * the project provides a web site, mailing lists and IRC
 * channels for your use.
 *
 * This program is free software, distributed under the terms of
 * the GNU General Public License Version 2. See the LICENSE file
 * at the top of the source tree.
 */

/*
 * Video codecs support for console_video.c
 * $Revision$
 */

/*** MODULEINFO
   <support_level>extended</support_level>
 ***/

#include "asterisk.h"
#include "console_video.h"
#include "asterisk/frame.h"
#include "asterisk/utils.h"   /* ast_calloc() */

struct video_out_desc;
struct video_dec_desc;
struct fbuf_t;

/*
 * Each codec is defined by a number of callbacks
 */
/*! \brief initialize the encoder */
typedef int (*encoder_init_f)(AVCodecContext *v);

/*! \brief actually call the encoder */
typedef int (*encoder_encode_f)(struct video_out_desc *v);

/*! \brief encapsulate the bistream in RTP frames */
typedef struct ast_frame *(*encoder_encap_f)(struct fbuf_t *, int mtu,
      struct ast_frame **tail);

/*! \brief inizialize the decoder */
typedef int (*decoder_init_f)(AVCodecContext *enc_ctx);

/*! \brief extract the bitstream from RTP frames and store in the fbuf.
 * return 0 if ok, 1 on error
 */
typedef int (*decoder_decap_f)(struct fbuf_t *b, uint8_t *data, int len);

/*! \brief actually call the decoder */
typedef int (*decoder_decode_f)(struct video_dec_desc *v, struct fbuf_t *b);

struct video_codec_desc {
   const char     *name;      /* format name */
   int         format;     /* AST_FORMAT_* */
   encoder_init_f    enc_init;
   encoder_encap_f      enc_encap;
   encoder_encode_f  enc_run;
   decoder_init_f    dec_init;
   decoder_decap_f      dec_decap;
   decoder_decode_f  dec_run;
};

/*
 * Descriptor for the incoming stream, with multiple buffers for the bitstream
 * extracted from the RTP packets, RTP reassembly info, and a frame buffer
 * for the decoded frame (buf).
 * The descriptor is allocated as the first frame comes in.
 *
 * Incoming payload is stored in one of the dec_in[] buffers, which are
 * emptied by the video thread. These buffers are organized in a circular
 * queue, with dec_in_cur being the buffer in use by the incoming stream,
 * and dec_in_dpy is the one being displayed. When the pointers need to
 * be changed, we synchronize the access to them with dec_lock.
 * When the list is full dec_in_cur = NULL (we cannot store new data),
 * when the list is empty dec_in_dpy = NULL (we cannot display frames).
 */
struct video_dec_desc {
   struct video_codec_desc *d_callbacks;  /* decoder callbacks */
   AVCodecContext          *dec_ctx;   /* information about the codec in the stream */
   AVCodec                 *codec;     /* reference to the codec */
   AVFrame                 *d_frame;   /* place to store the decoded frame */
   AVCodecParserContext    *parser;
   uint16_t       next_seq;   /* must be 16 bit */
   int                     discard; /* flag for discard status */
#define N_DEC_IN  3  /* number of incoming buffers */
   struct fbuf_t     *dec_in_cur;   /* buffer being filled in */
   struct fbuf_t     *dec_in_dpy;   /* buffer to display */
   struct fbuf_t dec_in[N_DEC_IN];  /* incoming bitstream, allocated/extended in fbuf_append() */
   struct fbuf_t dec_out;  /* decoded frame, no buffer (data is in AVFrame) */
};

#ifdef debugging_only

/* some debugging code to check the bitstream:
 * declare a bit buffer, initialize it, and fetch data from it.
 */
struct bitbuf {
   const uint8_t *base;
   int   bitsize; /* total size in bits */
   int   ofs;  /* next bit to read */
};

static struct bitbuf bitbuf_init(const uint8_t *base, int bitsize, int start_ofs)
{
   struct bitbuf a;
   a.base = base;
   a.bitsize = bitsize;
   a.ofs = start_ofs;
   return a;
}

static int bitbuf_left(struct bitbuf *b)
{
   return b->bitsize - b->ofs;
}

static uint32_t getbits(struct bitbuf *b, int n)
{
   int i, ofs;
   const uint8_t *d;
   uint8_t mask;
   uint32_t retval = 0;
   if (n> 31) {
      ast_log(LOG_WARNING, "too many bits %d, max 32\n", n);
      return 0;
   }
   if (n + b->ofs > b->bitsize) {
      ast_log(LOG_WARNING, "bitbuf overflow %d of %d\n", n + b->ofs, b->bitsize);
      n = b->bitsize - b->ofs;
   }
   ofs = 7 - b->ofs % 8;   /* start from msb */
   mask = 1 << ofs;
   d = b->base + b->ofs / 8;  /* current byte */
   for (i=0 ; i < n; i++) {
      retval += retval + (*d & mask ? 1 : 0);   /* shift in new byte */
      b->ofs++;
      mask >>= 1;
      if (mask == 0) {
         d++;
         mask = 0x80;
      }
   }
   return retval;
}

static void check_h261(struct fbuf_t *b)
{
   struct bitbuf a = bitbuf_init(b->data, b->used * 8, 0);
   uint32_t x, y;

   x = getbits(&a, 20); /* PSC, 0000 0000 0000 0001 0000 */
   if (x != 0x10) {
      ast_log(LOG_WARNING, "bad PSC 0x%x\n", x);
      return;
   }
   x = getbits(&a, 5);  /* temporal reference */
   y = getbits(&a, 6);  /* ptype */
   if (0)
   ast_log(LOG_WARNING, "size %d TR %d PTY spl %d doc %d freeze %d %sCIF hi %d\n",
      b->used,
      x,
      (y & 0x20) ? 1 : 0,
      (y & 0x10) ? 1 : 0,
      (y & 0x8) ? 1 : 0,
      (y & 0x4) ? "" : "Q",
      (y & 0x2) ? 1:0);
   while ( (x = getbits(&a, 1)) == 1)
      ast_log(LOG_WARNING, "PSPARE 0x%x\n", getbits(&a, 8));
   // ast_log(LOG_WARNING, "PSPARE 0 - start GOB LAYER\n");
   while ( (x = bitbuf_left(&a)) > 0) {
      // ast_log(LOG_WARNING, "GBSC %d bits left\n", x);
      x = getbits(&a, 16); /* GBSC 0000 0000 0000 0001 */
      if (x != 0x1) {
         ast_log(LOG_WARNING, "bad GBSC 0x%x\n", x);
         break;
      }
      x = getbits(&a, 4);  /* group number */
      y = getbits(&a, 5);  /* gquant */
      if (x == 0) {
         ast_log(LOG_WARNING, "  bad GN %d\n", x);
         break;
      }
      while ( (x = getbits(&a, 1)) == 1)
         ast_log(LOG_WARNING, "GSPARE 0x%x\n", getbits(&a, 8));
      while ( (x = bitbuf_left(&a)) > 0) { /* MB layer */
         break;
      }
   }
}

void dump_buf(struct fbuf_t *b);
void dump_buf(struct fbuf_t *b)
{
   int i, x, last2lines;
   char buf[80];

   last2lines = (b->used - 16) & ~0xf;
   ast_log(LOG_WARNING, "buf size %d of %d\n", b->used, b->size);
   for (i = 0; i < b->used; i++) {
      x = i & 0xf;
      if ( x == 0) { /* new line */
         if (i != 0)
            ast_log(LOG_WARNING, "%s\n", buf);
         memset(buf, '\0', sizeof(buf));
         sprintf(buf, "%04x: ", (unsigned)i);
      }
      sprintf(buf + 6 + x*3, "%02hhx ", b->data[i]);
      if (i > 31 && i < last2lines)
         i = last2lines - 1;
   }
   if (buf[0])
      ast_log(LOG_WARNING, "%s\n", buf);
}
#endif /* debugging_only */

/*!
 * Build an ast_frame for a given chunk of data, and link it into
 * the queue, with possibly 'head' bytes at the beginning to
 * fill in some fields later.
 */
static struct ast_frame *create_video_frame(uint8_t *start, uint8_t *end,
                  int format, int head, struct ast_frame *prev)
{
   int len = end-start;
   uint8_t *data;
   struct ast_frame *f;

   data = ast_calloc(1, len+head);
   f = ast_calloc(1, sizeof(*f));
   if (f == NULL || data == NULL) {
      ast_log(LOG_WARNING, "--- frame error f %p data %p len %d format %d\n",
            f, data, len, format);
      if (f)
         ast_free(f);
      if (data)
         ast_free(data);
      return NULL;
   }
   memcpy(data+head, start, len);
   f->data.ptr = data;
   f->mallocd = AST_MALLOCD_DATA | AST_MALLOCD_HDR;
   //f->has_timing_info = 1;
   //f->ts = ast_tvdiff_ms(ast_tvnow(), out->ts);
   f->datalen = len+head;
   f->frametype = AST_FRAME_VIDEO;
   f->subclass = format;
   f->samples = 0;
   f->offset = 0;
   f->src = "Console";
   f->delivery.tv_sec = 0;
   f->delivery.tv_usec = 0;
   f->seqno = 0;
   AST_LIST_NEXT(f, frame_list) = NULL;

   if (prev)
           AST_LIST_NEXT(prev, frame_list) = f;

   return f;
}


/*
 * Append a chunk of data to a buffer taking care of bit alignment
 * Return 0 on success, != 0 on failure
 */
static int fbuf_append(struct fbuf_t *b, uint8_t *src, int len,
   int sbit, int ebit)
{
   /*
    * Allocate buffer. ffmpeg wants an extra FF_INPUT_BUFFER_PADDING_SIZE,
    * and also wants 0 as a buffer terminator to prevent trouble.
    */
   int need = len + FF_INPUT_BUFFER_PADDING_SIZE;
   int i;
   uint8_t *dst, mask;

   if (b->data == NULL) {
      b->size = need;
      b->used = 0;
      b->ebit = 0;
      b->data = ast_calloc(1, b->size);
   } else if (b->used + need > b->size) {
      b->size = b->used + need;
      b->data = ast_realloc(b->data, b->size);
   }
   if (b->data == NULL) {
      ast_log(LOG_WARNING, "alloc failure for %d, discard\n",
         b->size);
      return 1;
   }
   if (b->used == 0 && b->ebit != 0) {
      ast_log(LOG_WARNING, "ebit not reset at start\n");
      b->ebit = 0;
   }
   dst = b->data + b->used;
   i = b->ebit + sbit;  /* bits to ignore around */
   if (i == 0) {  /* easy case, just append */
      /* do everything in the common block */
   } else if (i == 8) { /* easy too, just handle the overlap byte */
      mask = (1 << b->ebit) - 1;
      /* update the last byte in the buffer */
      dst[-1] &= ~mask; /* clear bits to ignore */
      dst[-1] |= (*src & mask);  /* append new bits */
      src += 1;   /* skip and prepare for common block */
      len --;
   } else { /* must shift the new block, not done yet */
      ast_log(LOG_WARNING, "must handle shift %d %d at %d\n",
         b->ebit, sbit, b->used);
      return 1;
   }
   memcpy(dst, src, len);
   b->used += len;
   b->ebit = ebit;
   b->data[b->used] = 0;   /* padding */
   return 0;
}

/*
 * Here starts the glue code for the various supported video codecs.
 * For each of them, we need to provide routines for initialization,
 * calling the encoder, encapsulating the bitstream in ast_frames,
 * extracting payload from ast_frames, and calling the decoder.
 */

/*--- h263+ support --- */

/*! \brief initialization of h263p */
static int h263p_enc_init(AVCodecContext *enc_ctx)
{
   /* modes supported are
   - Unrestricted Motion Vector (annex D)
   - Advanced Prediction (annex F)
   - Advanced Intra Coding (annex I)
   - Deblocking Filter (annex J)
   - Slice Structure (annex K)
   - Alternative Inter VLC (annex S)
   - Modified Quantization (annex T)
   */
   enc_ctx->flags |=CODEC_FLAG_H263P_UMV; /* annex D */
   enc_ctx->flags |=CODEC_FLAG_AC_PRED; /* annex f ? */
   enc_ctx->flags |=CODEC_FLAG_H263P_SLICE_STRUCT; /* annex k */
   enc_ctx->flags |= CODEC_FLAG_H263P_AIC; /* annex I */

   return 0;
}


/*
 * Create RTP/H.263 fragments to avoid IP fragmentation. We fragment on a
 * PSC or a GBSC, but if we don't find a suitable place just break somewhere.
 * Everything is byte-aligned.
 */
static struct ast_frame *h263p_encap(struct fbuf_t *b, int mtu,
   struct ast_frame **tail)
{
   struct ast_frame *cur = NULL, *first = NULL;
   uint8_t *d = b->data;
   int len = b->used;
   int l = len; /* size of the current fragment. If 0, must look for a psc */

   for (;len > 0; len -= l, d += l) {
      uint8_t *data;
      struct ast_frame *f;
      int i, h;

      if (len >= 3 && d[0] == 0 && d[1] == 0 && d[2] >= 0x80) {
         /* we are starting a new block, so look for a PSC. */
         for (i = 3; i < len - 3; i++) {
            if (d[i] == 0 && d[i+1] == 0 && d[i+2] >= 0x80) {
               l = i;
               break;
            }
         }
      }
      if (l > mtu || l > len) { /* psc not found, split */
         l = MIN(len, mtu);
      }
      if (l < 1 || l > mtu) {
         ast_log(LOG_WARNING, "--- frame error l %d\n", l);
         break;
      }

      if (d[0] == 0 && d[1] == 0) { /* we start with a psc */
         h = 0;
      } else { /* no psc, create a header */
         h = 2;
      }

      f = create_video_frame(d, d+l, AST_FORMAT_H263_PLUS, h, cur);
      if (!f)
         break;

      data = f->data.ptr;
      if (h == 0) {  /* we start with a psc */
         data[0] |= 0x04;  // set P == 1, and we are done
      } else { /* no psc, create a header */
         data[0] = data[1] = 0;  // P == 0
      }

      if (!cur)
         first = f;
      cur = f;
   }

   if (cur)
      cur->subclass |= 1; // RTP Marker

   *tail = cur;   /* end of the list */
   return first;
}

/*! \brief extract the bitstreem from the RTP payload.
 * This is format dependent.
 * For h263+, the format is defined in RFC 2429
 * and basically has a fixed 2-byte header as follows:
 * 5 bits   RR reserved, shall be 0
 * 1 bit P  indicate a start/end condition,
 *       in which case the payload should be prepended
 *       by two zero-valued bytes.
 * 1 bit V  there is an additional VRC header after this header
 * 6 bits   PLEN  length in bytes of extra picture header
 * 3 bits   PEBIT how many bits to be ignored in the last byte
 *
 * XXX the code below is not complete.
 */
static int h263p_decap(struct fbuf_t *b, uint8_t *data, int len)
{
   int PLEN;

   if (len < 2) {
      ast_log(LOG_WARNING, "invalid framesize %d\n", len);
      return 1;
   }
   PLEN = ( (data[0] & 1) << 5 ) | ( (data[1] & 0xf8) >> 3);

   if (PLEN > 0) {
      data += PLEN;
      len -= PLEN;
   }
   if (data[0] & 4)  /* bit P */
      data[0] = data[1] = 0;
   else {
      data += 2;
      len -= 2;
   }
   return fbuf_append(b, data, len, 0, 0);   /* ignore trail bits */
}


/*
 * generic encoder, used by the various protocols supported here.
 * We assume that the buffer is empty at the beginning.
 */
static int ffmpeg_encode(struct video_out_desc *v)
{
   struct fbuf_t *b = &v->enc_out;
   int i;

   b->used = avcodec_encode_video(v->enc_ctx, b->data, b->size, v->enc_in_frame);
   i = avcodec_encode_video(v->enc_ctx, b->data + b->used, b->size - b->used, NULL); /* delayed frames ? */
   if (i > 0) {
      ast_log(LOG_WARNING, "have %d more bytes\n", i);
      b->used += i;
   }
   return 0;
}

/*
 * Generic decoder, which is used by h263p, h263 and h261 as it simply
 * invokes ffmpeg's decoder.
 * av_parser_parse should merge a randomly chopped up stream into
 * proper frames. After that, if we have a valid frame, we decode it
 * until the entire frame is processed.
 */
static int ffmpeg_decode(struct video_dec_desc *v, struct fbuf_t *b)
{
   uint8_t *src = b->data;
   int srclen = b->used;
   int full_frame = 0;

   if (srclen == 0)  /* no data */
      return 0;
   while (srclen) {
      uint8_t *data;
      int datalen, ret;
      int len = av_parser_parse(v->parser, v->dec_ctx, &data, &datalen, src, srclen, 0, 0);

      src += len;
      srclen -= len;
      /* The parser might return something it cannot decode, so it skips
       * the block returning no data
       */
      if (data == NULL || datalen == 0)
         continue;
      ret = avcodec_decode_video(v->dec_ctx, v->d_frame, &full_frame, data, datalen);
      if (full_frame == 1) /* full frame */
         break;
      if (ret < 0) {
         ast_log(LOG_NOTICE, "Error decoding\n");
         break;
      }
   }
   if (srclen != 0)  /* update b with leftover data */
      memmove(b->data, src, srclen);
   b->used = srclen;
   b->ebit = 0;
   return full_frame;
}

static struct video_codec_desc h263p_codec = {
   .name = "h263p",
   .format = AST_FORMAT_H263_PLUS,
   .enc_init = h263p_enc_init,
   .enc_encap = h263p_encap,
   .enc_run = ffmpeg_encode,
   .dec_init = NULL,
   .dec_decap = h263p_decap,
   .dec_run = ffmpeg_decode
};

/*--- Plain h263 support --------*/

static int h263_enc_init(AVCodecContext *enc_ctx)
{
   /* XXX check whether these are supported */
   enc_ctx->flags |= CODEC_FLAG_H263P_UMV;
   enc_ctx->flags |= CODEC_FLAG_H263P_AIC;
   enc_ctx->flags |= CODEC_FLAG_H263P_SLICE_STRUCT;
   enc_ctx->flags |= CODEC_FLAG_AC_PRED;

   return 0;
}

/*
 * h263 encapsulation is specified in RFC2190. There are three modes
 * defined (A, B, C), with 4, 8 and 12 bytes of header, respectively.
 * The header is made as follows
 *     0.....................|.......................|.............|....31
 * F:1 P:1 SBIT:3 EBIT:3 SRC:3 I:1 U:1 S:1 A:1 R:4 DBQ:2 TRB:3 TR:8
 * FP = 0- mode A, (only one word of header)
 * FP = 10 mode B, and also means this is an I or P frame
 * FP = 11 mode C, and also means this is a PB frame.
 * SBIT, EBIT nuber of bits to ignore at beginning (msbits) and end (lsbits)
 * SRC  bits 6,7,8 from the h263 PTYPE field
 * I = 0 intra-coded, 1 = inter-coded (bit 9 from PTYPE)
 * U = 1 for Unrestricted Motion Vector (bit 10 from PTYPE)
 * S = 1 for Syntax Based Arith coding (bit 11 from PTYPE)
 * A = 1 for Advanced Prediction (bit 12 from PTYPE)
 * R = reserved, must be 0
 * DBQ = differential quantization, DBQUANT from h263, 0 unless we are using
 * PB frames
 * TRB = temporal reference for bframes, also 0 unless this is a PB frame
 * TR = temporal reference for P frames, also 0 unless PB frame.
 *
 * Mode B and mode C description omitted.
 *
 * An RTP frame can start with a PSC 0000 0000 0000 0000 1000 0
 * or with a GBSC, which also has the first 17 bits as a PSC.
 * Note - PSC are byte-aligned, GOB not necessarily. PSC start with
 * PSC:22 0000 0000 0000 0000 1000 00  picture start code
 * TR:8   .... ....        temporal reference
 *      PTYPE:13 or more         ptype...
 * If we don't fragment a GOB SBIT and EBIT = 0.
 * reference, 8 bit)
 *
 * The assumption below is that we start with a PSC.
 */
static struct ast_frame *h263_encap(struct fbuf_t *b, int mtu,
      struct ast_frame **tail)
{
   uint8_t *d = b->data;
   int start = 0, i, len = b->used;
   struct ast_frame *f, *cur = NULL, *first = NULL;
   const int pheader_len = 4; /* Use RFC-2190 Mode A */
   uint8_t h263_hdr[12];   /* worst case, room for a type c header */
   uint8_t *h = h263_hdr;  /* shorthand */

#define H263_MIN_LEN 6
   if (len < H263_MIN_LEN) /* unreasonably small */
      return NULL;

   memset(h263_hdr, '\0', sizeof(h263_hdr));
   /* Now set the header bytes. Only type A by now,
    * and h[0] = h[2] = h[3] = 0 by default.
    * PTYPE starts 30 bits in the picture, so the first useful
    * bit for us is bit 36 i.e. within d[4] (0 is the msbit).
    * SRC = d[4] & 0x1c goes into data[1] & 0xe0
    * I   = d[4] & 0x02 goes into data[1] & 0x10
    * U   = d[4] & 0x01 goes into data[1] & 0x08
    * S   = d[5] & 0x80 goes into data[1] & 0x04
    * A   = d[5] & 0x40 goes into data[1] & 0x02
    * R   = 0           goes into data[1] & 0x01
    * Optimizing it, we have
    */
   h[1] = ( (d[4] & 0x1f) << 3 ) |  /* SRC, I, U */
      ( (d[5] & 0xc0) >> 5 );    /* S, A, R */

   /* now look for the next PSC or GOB header. First try to hit
    * a '0' byte then look around for the 0000 0000 0000 0000 1 pattern
    * which is both in the PSC and the GBSC.
    */
   for (i = H263_MIN_LEN, start = 0; start < len; start = i, i += 3) {
      //ast_log(LOG_WARNING, "search at %d of %d/%d\n", i, start, len);
      for (; i < len ; i++) {
         uint8_t x, rpos, lpos;
         int rpos_i; /* index corresponding to rpos */
         if (d[i] != 0)    /* cannot be in a GBSC */
            continue;
         if (i > len - 1)
            break;
         x = d[i+1];
         if (x == 0) /* next is equally good */
            continue;
         /* see if around us we can make 16 '0' bits for the GBSC.
          * Look for the first bit set on the right, and then
          * see if we have enough 0 on the left.
          * We are guaranteed to end before rpos == 0
          */
         for (rpos = 0x80, rpos_i = 8; rpos; rpos >>= 1, rpos_i--)
            if (x & rpos)  /* found the '1' bit in GBSC */
               break;
         x = d[i-1];    /* now look behind */
         for (lpos = rpos; lpos ; lpos >>= 1)
            if (x & lpos)  /* too early, not a GBSC */
               break;
         if (lpos)      /* as i said... */
            continue;
         /* now we have a GBSC starting somewhere in d[i-1],
          * but it might be not byte-aligned
          */
         if (rpos == 0x80) {  /* lucky case */
            i = i - 1;
         } else { /* XXX to be completed */
            ast_log(LOG_WARNING, "unaligned GBSC 0x%x %d\n",
               rpos, rpos_i);
         }
         break;
      }
      /* This frame is up to offset i (not inclusive).
       * We do not split it yet even if larger than MTU.
       */
      f = create_video_frame(d + start, d+i, AST_FORMAT_H263,
            pheader_len, cur);

      if (!f)
         break;
      memmove(f->data.ptr, h, 4);   /* copy the h263 header */
      /* XXX to do: if not aligned, fix sbit and ebit,
       * then move i back by 1 for the next frame
       */
      if (!cur)
         first = f;
      cur = f;
   }

   if (cur)
      cur->subclass |= 1;  // RTP Marker

   *tail = cur;
   return first;
}

/* XXX We only drop the header here, but maybe we need more. */
static int h263_decap(struct fbuf_t *b, uint8_t *data, int len)
{
   if (len < 4) {
      ast_log(LOG_WARNING, "invalid framesize %d\n", len);
      return 1;   /* error */
   }

   if ( (data[0] & 0x80) == 0) {
      len -= 4;
      data += 4;
   } else {
      ast_log(LOG_WARNING, "unsupported mode 0x%x\n",
         data[0]);
      return 1;
   }
   return fbuf_append(b, data, len, 0, 0);   /* XXX no bit alignment support yet */
}

static struct video_codec_desc h263_codec = {
   .name = "h263",
   .format = AST_FORMAT_H263,
   .enc_init = h263_enc_init,
   .enc_encap = h263_encap,
   .enc_run = ffmpeg_encode,
   .dec_init = NULL,
   .dec_decap = h263_decap,
   .dec_run = ffmpeg_decode

};

/*---- h261 support -----*/
static int h261_enc_init(AVCodecContext *enc_ctx)
{
   /* It is important to set rtp_payload_size = 0, otherwise
    * ffmpeg in h261 mode will produce output that it cannot parse.
    * Also try to send I frames more frequently than with other codecs.
    */
   enc_ctx->rtp_payload_size = 0; /* important - ffmpeg fails otherwise */

   return 0;
}

/*
 * The encapsulation of H261 is defined in RFC4587 which obsoletes RFC2032
 * The bitstream is preceded by a 32-bit header word:
 *  SBIT:3 EBIT:3 I:1 V:1 GOBN:4 MBAP:5 QUANT:5 HMVD:5 VMVD:5
 * SBIT and EBIT are the bits to be ignored at beginning and end,
 * I=1 if the stream has only INTRA frames - cannot change during the stream.
 * V=0 if motion vector is not used. Cannot change.
 * GOBN is the GOB number in effect at the start of packet, 0 if we
 * start with a GOB header
 * QUANT is the quantizer in effect, 0 if we start with GOB header
 * HMVD  reference horizontal motion vector. 10000 is forbidden
 * VMVD  reference vertical motion vector, as above.
 * Packetization should occur at GOB boundaries, and if not possible
 * with MacroBlock fragmentation. However it is likely that blocks
 * are not bit-aligned so we must take care of this.
 */
static struct ast_frame *h261_encap(struct fbuf_t *b, int mtu,
      struct ast_frame **tail)
{
   uint8_t *d = b->data;
   int start = 0, i, len = b->used;
   struct ast_frame *f, *cur = NULL, *first = NULL;
   const int pheader_len = 4;
   uint8_t h261_hdr[4];
   uint8_t *h = h261_hdr;  /* shorthand */
   int sbit = 0, ebit = 0;

#define H261_MIN_LEN 10
   if (len < H261_MIN_LEN) /* unreasonably small */
      return NULL;

   memset(h261_hdr, '\0', sizeof(h261_hdr));

   /* Similar to the code in h263_encap, but the marker there is longer.
    * Start a few bytes within the bitstream to avoid hitting the marker
    * twice. Note we might access the buffer at len, but this is ok because
    * the caller has it oversized.
    */
   for (i = H261_MIN_LEN, start = 0; start < len - 1; start = i, i += 4) {
#if 0 /* test - disable packetization */
      i = len; /* wrong... */
#else
      int found = 0, found_ebit = 0;   /* last GBSC position found */
      for (; i < len ; i++) {
         uint8_t x, rpos, lpos;
         if (d[i] != 0)    /* cannot be in a GBSC */
            continue;
         x = d[i+1];
         if (x == 0) /* next is equally good */
            continue;
         /* See if around us we find 15 '0' bits for the GBSC.
          * Look for the first bit set on the right, and then
          * see if we have enough 0 on the left.
          * We are guaranteed to end before rpos == 0
          */
         for (rpos = 0x80, ebit = 7; rpos; ebit--, rpos >>= 1)
            if (x & rpos)  /* found the '1' bit in GBSC */
               break;
         x = d[i-1];    /* now look behind */
         for (lpos = (rpos >> 1); lpos ; lpos >>= 1)
            if (x & lpos)  /* too early, not a GBSC */
               break;
         if (lpos)      /* as i said... */
            continue;
         /* now we have a GBSC starting somewhere in d[i-1],
          * but it might be not byte-aligned. Just remember it.
          */
         if (i - start > mtu) /* too large, stop now */
            break;
         found_ebit = ebit;
         found = i;
         i += 4;  /* continue forward */
      }
      if (i >= len) {   /* trim if we went too forward */
         i = len;
         ebit = 0;   /* hopefully... should ask the bitstream ? */
      }
      if (i - start > mtu && found) {
         /* use the previous GBSC, hope is within the mtu */
         i = found;
         ebit = found_ebit;
      }
#endif /* test */
      if (i - start < 4)   /* XXX too short ? */
         continue;
      /* This frame is up to offset i (not inclusive).
       * We do not split it yet even if larger than MTU.
       */
      f = create_video_frame(d + start, d+i, AST_FORMAT_H261,
            pheader_len, cur);

      if (!f)
         break;
      /* recompute header with I=0, V=1 */
      h[0] = ( (sbit & 7) << 5 ) | ( (ebit & 7) << 2 ) | 1;
      memmove(f->data.ptr, h, 4);   /* copy the h261 header */
      if (ebit)   /* not aligned, restart from previous byte */
         i--;
      sbit = (8 - ebit) & 7;
      ebit = 0;
      if (!cur)
         first = f;
      cur = f;
   }
   if (cur)
      cur->subclass |= 1;  // RTP Marker

   *tail = cur;
   return first;
}

/*
 * Pieces might be unaligned so we really need to put them together.
 */
static int h261_decap(struct fbuf_t *b, uint8_t *data, int len)
{
   int ebit, sbit;

   if (len < 8) {
      ast_log(LOG_WARNING, "invalid framesize %d\n", len);
      return 1;
   }
   sbit = (data[0] >> 5) & 7;
   ebit = (data[0] >> 2) & 7;
   len -= 4;
   data += 4;
   return fbuf_append(b, data, len, sbit, ebit);
}

static struct video_codec_desc h261_codec = {
   .name = "h261",
   .format = AST_FORMAT_H261,
   .enc_init = h261_enc_init,
   .enc_encap = h261_encap,
   .enc_run = ffmpeg_encode,
   .dec_init = NULL,
   .dec_decap = h261_decap,
   .dec_run = ffmpeg_decode
};

/* mpeg4 support */
static int mpeg4_enc_init(AVCodecContext *enc_ctx)
{
#if 0
   //enc_ctx->flags |= CODEC_FLAG_LOW_DELAY; /*don't use b frames ?*/
   enc_ctx->flags |= CODEC_FLAG_AC_PRED;
   enc_ctx->flags |= CODEC_FLAG_H263P_UMV;
   enc_ctx->flags |= CODEC_FLAG_QPEL;
   enc_ctx->flags |= CODEC_FLAG_4MV;
   enc_ctx->flags |= CODEC_FLAG_GMC;
   enc_ctx->flags |= CODEC_FLAG_LOOP_FILTER;
   enc_ctx->flags |= CODEC_FLAG_H263P_SLICE_STRUCT;
#endif
   enc_ctx->rtp_payload_size = 0; /* important - ffmpeg fails otherwise */
   return 0;
}

/* simplistic encapsulation - just split frames in mtu-size units */
static struct ast_frame *mpeg4_encap(struct fbuf_t *b, int mtu,
   struct ast_frame **tail)
{
   struct ast_frame *f, *cur = NULL, *first = NULL;
   uint8_t *d = b->data;
   uint8_t *end = d + b->used;
   int len;

   for (;d < end; d += len, cur = f) {
      len = MIN(mtu, end - d);
      f = create_video_frame(d, d + len, AST_FORMAT_MP4_VIDEO, 0, cur);
      if (!f)
         break;
      if (!first)
         first = f;
   }
   if (cur)
      cur->subclass |= 1;
   *tail = cur;
   return first;
}

static int mpeg4_decap(struct fbuf_t *b, uint8_t *data, int len)
{
   return fbuf_append(b, data, len, 0, 0);
}

static int mpeg4_decode(struct video_dec_desc *v, struct fbuf_t *b)
{
   int full_frame = 0, datalen = b->used;
   int ret = avcodec_decode_video(v->dec_ctx, v->d_frame, &full_frame,
      b->data, datalen);
   if (ret < 0) {
      ast_log(LOG_NOTICE, "Error decoding\n");
      ret = datalen; /* assume we used everything. */
   }
   datalen -= ret;
   if (datalen > 0)  /* update b with leftover bytes */
      memmove(b->data, b->data + ret, datalen);
   b->used = datalen;
   b->ebit = 0;
   return full_frame;
}

static struct video_codec_desc mpeg4_codec = {
   .name = "mpeg4",
   .format = AST_FORMAT_MP4_VIDEO,
   .enc_init = mpeg4_enc_init,
   .enc_encap = mpeg4_encap,
   .enc_run = ffmpeg_encode,
   .dec_init = NULL,
   .dec_decap = mpeg4_decap,
   .dec_run = mpeg4_decode
};

static int h264_enc_init(AVCodecContext *enc_ctx)
{
   enc_ctx->flags |= CODEC_FLAG_TRUNCATED;
   //enc_ctx->flags |= CODEC_FLAG_GLOBAL_HEADER;
   //enc_ctx->flags2 |= CODEC_FLAG2_FASTPSKIP;
   /* TODO: Maybe we need to add some other flags */
   enc_ctx->rtp_mode = 0;
   enc_ctx->rtp_payload_size = 0;
   enc_ctx->bit_rate_tolerance = enc_ctx->bit_rate;
   return 0;
}

static int h264_dec_init(AVCodecContext *dec_ctx)
{
   dec_ctx->flags |= CODEC_FLAG_TRUNCATED;

   return 0;
}

/*
 * The structure of a generic H.264 stream is:
 * - 0..n 0-byte(s), unused, optional. one zero-byte is always present
 *   in the first NAL before the start code prefix.
 * - start code prefix (3 bytes): 0x000001
 *   (the first bytestream has a
 *   like these 0x00000001!)
 * - NAL header byte ( F[1] | NRI[2] | Type[5] ) where type != 0
 * - byte-stream
 * - 0..n 0-byte(s) (padding, unused).
 * Segmentation in RTP only needs to be done on start code prefixes.
 * If fragments are too long... we don't support it yet.
 * - encapsulate (or fragment) the byte-stream (with NAL header included)
 */
static struct ast_frame *h264_encap(struct fbuf_t *b, int mtu,
   struct ast_frame **tail)
{
   struct ast_frame *f = NULL, *cur = NULL, *first = NULL;
   uint8_t *d, *start = b->data;
   uint8_t *end = start + b->used;

   /* Search the first start code prefix - ITU-T H.264 sec. B.2,
    * and move start right after that, on the NAL header byte.
    */
#define HAVE_NAL(x) (x[-4] == 0 && x[-3] == 0 && x[-2] == 0 && x[-1] == 1)
   for (start += 4; start < end; start++) {
      int ty = start[0] & 0x1f;
      if (HAVE_NAL(start) && ty != 0 && ty != 31)
         break;
   }
   /* if not found, or too short, we just skip the next loop and are done. */

   /* Here follows the main loop to create frames. Search subsequent start
    * codes, and then possibly fragment the unit into smaller fragments.
    */
   for (;start < end - 4; start = d) {
   int size;      /* size of current block */
   uint8_t hdr[2];      /* add-on header when fragmenting */
   int ty = 0;

   /* now search next nal */
   for (d = start + 4; d < end; d++) {
      ty = d[0] & 0x1f;
      if (HAVE_NAL(d))
         break;   /* found NAL */
   }
   /* have a block to send. d past the start code unless we overflow */
   if (d >= end) {   /* NAL not found */
      d = end + 4;
   } else if (ty == 0 || ty == 31) { /* found but invalid type, skip */
      ast_log(LOG_WARNING, "skip invalid nal type %d at %d of %d\n",
         ty, d - (uint8_t *)b->data, b->used);
      continue;
   }

   size = d - start - 4;   /* don't count the end */

   if (size < mtu) { // test - don't fragment
      // Single NAL Unit
      f = create_video_frame(start, d - 4, AST_FORMAT_H264, 0, cur);
      if (!f)
         break;
      if (!first)
         first = f;

      cur = f;
      continue;
   }

   // Fragmented Unit (Mode A: no DON, very weak)
   hdr[0] = (*start & 0xe0) | 28;   /* mark as a fragmentation unit */
   hdr[1] = (*start++ & 0x1f) | 0x80 ; /* keep type and set START bit */
   size--;     /* skip the NAL header */
   while (size) {
      uint8_t *data;
      int frag_size = MIN(size, mtu);

      f = create_video_frame(start, start+frag_size, AST_FORMAT_H264, 2, cur);
      if (!f)
         break;
      size -= frag_size;   /* skip this data block */
      start += frag_size;

      data = f->data.ptr;
      data[0] = hdr[0];
      data[1] = hdr[1] | (size == 0 ? 0x40 : 0);   /* end bit if we are done */
      hdr[1] &= ~0x80;  /* clear start bit for subsequent frames */
      if (!first)
         first = f;
      cur = f;
   }
    }

   if (cur)
      cur->subclass |= 1;     // RTP Marker

   *tail = cur;

   return first;
}

static int h264_decap(struct fbuf_t *b, uint8_t *data, int len)
{
   /* Start Code Prefix (Annex B in specification) */
   uint8_t scp[] = { 0x00, 0x00, 0x00, 0x01 };
   int retval = 0;
   int type, ofs = 0;

   if (len < 2) {
      ast_log(LOG_WARNING, "--- invalid len %d\n", len);
      return 1;
   }
   /* first of all, check if the packet has F == 0 */
   if (data[0] & 0x80) {
      ast_log(LOG_WARNING, "--- forbidden packet; nal: %02hhx\n",
         data[0]);
      return 1;
   }

   type = data[0] & 0x1f;
   switch (type) {
   case 0:
   case 31:
      ast_log(LOG_WARNING, "--- invalid type: %d\n", type);
      return 1;
   case 24:
   case 25:
   case 26:
   case 27:
   case 29:
      ast_log(LOG_WARNING, "--- encapsulation not supported : %d\n", type);
      return 1;
   case 28: /* FU-A Unit */
      if (data[1] & 0x80) { // S == 1, import F and NRI from next
         data[1] &= 0x1f;  /* preserve type */
         data[1] |= (data[0] & 0xe0);  /* import F & NRI */
         retval = fbuf_append(b, scp, sizeof(scp), 0, 0);
         ofs = 1;
      } else {
         ofs = 2;
      }
      break;
   default: /* From 1 to 23 (Single NAL Unit) */
      retval = fbuf_append(b, scp, sizeof(scp), 0, 0);
   }
   if (!retval)
      retval = fbuf_append(b, data + ofs, len - ofs, 0, 0);
   if (retval)
      ast_log(LOG_WARNING, "result %d\n", retval);
   return retval;
}

static struct video_codec_desc h264_codec = {
   .name = "h264",
   .format = AST_FORMAT_H264,
   .enc_init = h264_enc_init,
   .enc_encap = h264_encap,
   .enc_run = ffmpeg_encode,
   .dec_init = h264_dec_init,
   .dec_decap = h264_decap,
   .dec_run = ffmpeg_decode
};

/*
 * Table of translation between asterisk and ffmpeg formats.
 * We need also a field for read and write (encoding and decoding), because
 * e.g. H263+ uses different codec IDs in ffmpeg when encoding or decoding.
 */
struct _cm {    /* map ffmpeg codec types to asterisk formats */
   uint32_t ast_format; /* 0 is a terminator */
   enum CodecID   codec;
   enum { CM_RD = 1, CM_WR = 2, CM_RDWR = 3 } rw;  /* read or write or both ? */
   //struct video_codec_desc *codec_desc;
};

static const struct _cm video_formats[] = {
        { AST_FORMAT_H263_PLUS, CODEC_ID_H263,  CM_RD }, /* incoming H263P ? */
        { AST_FORMAT_H263_PLUS, CODEC_ID_H263P, CM_WR },
        { AST_FORMAT_H263,      CODEC_ID_H263,  CM_RD },
        { AST_FORMAT_H263,      CODEC_ID_H263,  CM_WR },
        { AST_FORMAT_H261,      CODEC_ID_H261,  CM_RDWR },
        { AST_FORMAT_H264,      CODEC_ID_H264,  CM_RDWR },
        { AST_FORMAT_MP4_VIDEO, CODEC_ID_MPEG4, CM_RDWR },
        { 0,                    0, 0 },
};


/*! \brief map an asterisk format into an ffmpeg one */
static enum CodecID map_video_format(uint32_t ast_format, int rw)
{
   struct _cm *i;

   for (i = video_formats; i->ast_format != 0; i++)
      if (ast_format & i->ast_format && rw & i->rw) {
         return i->codec;
      }
   return CODEC_ID_NONE;
}

/* pointers to supported codecs. We assume the first one to be non null. */
static const struct video_codec_desc *supported_codecs[] = {
   &h263p_codec,
   &h264_codec,
   &h263_codec,
   &h261_codec,
   &mpeg4_codec,
   NULL
};

/*
 * Map the AST_FORMAT to the library. If not recognised, fail.
 * This is useful in the input path where we get frames.
 */
static struct video_codec_desc *map_video_codec(int fmt)
{
   int i;

   for (i = 0; supported_codecs[i]; i++)
      if (fmt == supported_codecs[i]->format) {
         ast_log(LOG_WARNING, "using %s for format 0x%x\n",
            supported_codecs[i]->name, fmt);
         return supported_codecs[i];
      }
   return NULL;
}

/*! \brief uninitialize the descriptor for remote video stream */
static struct video_dec_desc *dec_uninit(struct video_dec_desc *v)
{
   int i;

   if (v == NULL)    /* not initialized yet */
      return NULL;
   if (v->parser) {
      av_parser_close(v->parser);
      v->parser = NULL;
   }
   if (v->dec_ctx) {
      avcodec_close(v->dec_ctx);
      av_free(v->dec_ctx);
      v->dec_ctx = NULL;
   }
   if (v->d_frame) {
      av_free(v->d_frame);
      v->d_frame = NULL;
   }
   v->codec = NULL;  /* only a reference */
   v->d_callbacks = NULL;     /* forget the decoder */
   v->discard = 1;      /* start in discard mode */
   for (i = 0; i < N_DEC_IN; i++)
      fbuf_free(&v->dec_in[i]);
   fbuf_free(&v->dec_out);
   ast_free(v);
   return NULL;   /* error, in case someone cares */
}

/*
 * initialize ffmpeg resources used for decoding frames from the network.
 */
static struct video_dec_desc *dec_init(uint32_t the_ast_format)
{
   enum CodecID codec;
   struct video_dec_desc *v = ast_calloc(1, sizeof(*v));
   if (v == NULL)
      return NULL;

   v->discard = 1;

   v->d_callbacks = map_video_codec(the_ast_format);
   if (v->d_callbacks == NULL) {
      ast_log(LOG_WARNING, "cannot find video codec, drop input 0x%x\n", the_ast_format);
      return dec_uninit(v);
   }

   codec = map_video_format(v->d_callbacks->format, CM_RD);

   v->codec = avcodec_find_decoder(codec);
   if (!v->codec) {
      ast_log(LOG_WARNING, "Unable to find the decoder for format %d\n", codec);
      return dec_uninit(v);
   }
   /*
    * Initialize the codec context.
    */
   v->dec_ctx = avcodec_alloc_context();
   if (!v->dec_ctx) {
      ast_log(LOG_WARNING, "Cannot allocate the decoder context\n");
      return dec_uninit(v);
   }
   /* XXX call dec_init() ? */
   if (avcodec_open(v->dec_ctx, v->codec) < 0) {
      ast_log(LOG_WARNING, "Cannot open the decoder context\n");
      av_free(v->dec_ctx);
      v->dec_ctx = NULL;
      return dec_uninit(v);
   }

   v->parser = av_parser_init(codec);
   if (!v->parser) {
      ast_log(LOG_WARNING, "Cannot initialize the decoder parser\n");
      return dec_uninit(v);
   }

   v->d_frame = avcodec_alloc_frame();
   if (!v->d_frame) {
      ast_log(LOG_WARNING, "Cannot allocate decoding video frame\n");
      return dec_uninit(v);
   }
        v->dec_in_cur = &v->dec_in[0]; /* buffer for incoming frames */
        v->dec_in_dpy = NULL;      /* nothing to display */

   return v;   /* ok */
}
/*------ end codec specific code -----*/