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 -----*/