rtpenc: packetizer for VC-2 HQ RTP payload format (draft v1)
[ffmpeg.git] / libavformat / sdp.c
index 8c831f3..8279d59 100644 (file)
@@ -29,6 +29,7 @@
 #include "avformat.h"
 #include "internal.h"
 #include "avc.h"
+#include "hevc.h"
 #include "rtp.h"
 #if CONFIG_NETWORK
 #include "network.h"
@@ -150,60 +151,45 @@ static int sdp_get_address(char *dest_addr, int size, int *ttl, const char *url)
 }
 
 #define MAX_PSET_SIZE 1024
-static char *extradata2psets(AVCodecContext *c)
+static char *extradata2psets(AVFormatContext *s, AVCodecParameters *par)
 {
     char *psets, *p;
     const uint8_t *r;
     static const char pset_string[] = "; sprop-parameter-sets=";
     static const char profile_string[] = "; profile-level-id=";
-    uint8_t *orig_extradata = NULL;
-    int orig_extradata_size = 0;
+    uint8_t *extradata = par->extradata;
+    int extradata_size = par->extradata_size;
+    uint8_t *tmpbuf = NULL;
     const uint8_t *sps = NULL, *sps_end;
 
-    if (c->extradata_size > MAX_EXTRADATA_SIZE) {
-        av_log(c, AV_LOG_ERROR, "Too much extradata!\n");
+    if (par->extradata_size > MAX_EXTRADATA_SIZE) {
+        av_log(s, AV_LOG_ERROR, "Too much extradata!\n");
 
         return NULL;
     }
-    if (c->extradata[0] == 1) {
-        uint8_t *dummy_p;
-        int dummy_int;
-        AVBitStreamFilterContext *bsfc= av_bitstream_filter_init("h264_mp4toannexb");
-
-        if (!bsfc) {
-            av_log(c, AV_LOG_ERROR, "Cannot open the h264_mp4toannexb BSF!\n");
-
-            return NULL;
-        }
-
-        orig_extradata_size = c->extradata_size;
-        orig_extradata = av_mallocz(orig_extradata_size +
-                                    FF_INPUT_BUFFER_PADDING_SIZE);
-        if (!orig_extradata) {
-            av_bitstream_filter_close(bsfc);
+    if (par->extradata[0] == 1) {
+        if (ff_avc_write_annexb_extradata(par->extradata, &extradata,
+                                          &extradata_size))
             return NULL;
-        }
-        memcpy(orig_extradata, c->extradata, orig_extradata_size);
-        av_bitstream_filter_filter(bsfc, c, NULL, &dummy_p, &dummy_int, NULL, 0, 0);
-        av_bitstream_filter_close(bsfc);
+        tmpbuf = extradata;
     }
 
     psets = av_mallocz(MAX_PSET_SIZE);
     if (!psets) {
-        av_log(c, AV_LOG_ERROR, "Cannot allocate memory for the parameter sets.\n");
-        av_free(orig_extradata);
+        av_log(s, AV_LOG_ERROR, "Cannot allocate memory for the parameter sets.\n");
+        av_free(tmpbuf);
         return NULL;
     }
     memcpy(psets, pset_string, strlen(pset_string));
     p = psets + strlen(pset_string);
-    r = ff_avc_find_startcode(c->extradata, c->extradata + c->extradata_size);
-    while (r < c->extradata + c->extradata_size) {
+    r = ff_avc_find_startcode(extradata, extradata + extradata_size);
+    while (r < extradata + extradata_size) {
         const uint8_t *r1;
         uint8_t nal_type;
 
         while (!*(r++));
         nal_type = *r & 0x1f;
-        r1 = ff_avc_find_startcode(r, c->extradata + c->extradata_size);
+        r1 = ff_avc_find_startcode(r, extradata + extradata_size);
         if (nal_type != 7 && nal_type != 8) { /* Only output SPS and PPS */
             r = r1;
             continue;
@@ -217,8 +203,9 @@ static char *extradata2psets(AVCodecContext *c)
             sps_end = r1;
         }
         if (!av_base64_encode(p, MAX_PSET_SIZE - (p - psets), r, r1 - r)) {
-            av_log(c, AV_LOG_ERROR, "Cannot Base64-encode %"PTRDIFF_SPECIFIER" %"PTRDIFF_SPECIFIER"!\n", MAX_PSET_SIZE - (p - psets), r1 - r);
+            av_log(s, AV_LOG_ERROR, "Cannot Base64-encode %"PTRDIFF_SPECIFIER" %"PTRDIFF_SPECIFIER"!\n", MAX_PSET_SIZE - (p - psets), r1 - r);
             av_free(psets);
+            av_free(tmpbuf);
 
             return NULL;
         }
@@ -231,44 +218,141 @@ static char *extradata2psets(AVCodecContext *c)
         ff_data_to_hex(p, sps + 1, 3, 0);
         p[6] = '\0';
     }
-    if (orig_extradata) {
-        av_free(c->extradata);
-        c->extradata      = orig_extradata;
-        c->extradata_size = orig_extradata_size;
+    av_free(tmpbuf);
+
+    return psets;
+}
+
+static char *extradata2psets_hevc(AVCodecParameters *par)
+{
+    char *psets;
+    uint8_t *extradata = par->extradata;
+    int extradata_size = par->extradata_size;
+    uint8_t *tmpbuf = NULL;
+    int ps_pos[3] = { 0 };
+    static const char * const ps_names[3] = { "vps", "sps", "pps" };
+    int num_arrays, num_nalus;
+    int pos, i, j;
+
+    // Convert to hvcc format. Since we need to group multiple NALUs of
+    // the same type, and we might need to convert from one format to the
+    // other anyway, we get away with a little less work by using the hvcc
+    // format.
+    if (par->extradata[0] != 1) {
+        AVIOContext *pb;
+        if (avio_open_dyn_buf(&pb) < 0)
+            return NULL;
+        if (ff_isom_write_hvcc(pb, par->extradata, par->extradata_size, 0) < 0) {
+            avio_close_dyn_buf(pb, &tmpbuf);
+            goto err;
+        }
+        extradata_size = avio_close_dyn_buf(pb, &extradata);
+        tmpbuf = extradata;
+    }
+
+    if (extradata_size < 23)
+        goto err;
+
+    num_arrays = extradata[22];
+    pos = 23;
+    for (i = 0; i < num_arrays; i++) {
+        int num_nalus, nalu_type;
+        if (pos + 3 > extradata_size)
+            goto err;
+        nalu_type = extradata[pos] & 0x3f;
+        // Not including libavcodec/hevc.h to avoid confusion between
+        // NAL_* with the same name for both H264 and HEVC.
+        if (nalu_type == 32) // VPS
+            ps_pos[0] = pos;
+        else if (nalu_type == 33) // SPS
+            ps_pos[1] = pos;
+        else if (nalu_type == 34) // PPS
+            ps_pos[2] = pos;
+        num_nalus = AV_RB16(&extradata[pos + 1]);
+        pos += 3;
+        for (j = 0; j < num_nalus; j++) {
+            int len;
+            if (pos + 2 > extradata_size)
+                goto err;
+            len = AV_RB16(&extradata[pos]);
+            pos += 2;
+            if (pos + len > extradata_size)
+                goto err;
+            pos += len;
+        }
     }
+    if (!ps_pos[0] || !ps_pos[1] || !ps_pos[2])
+        goto err;
+
+    psets = av_mallocz(MAX_PSET_SIZE);
+    if (!psets)
+        goto err;
+    psets[0] = '\0';
+
+    for (i = 0; i < 3; i++) {
+        pos = ps_pos[i];
+
+        if (i > 0)
+            av_strlcat(psets, "; ", MAX_PSET_SIZE);
+        av_strlcatf(psets, MAX_PSET_SIZE, "sprop-%s=", ps_names[i]);
+
+        // Skipping boundary checks in the input here; we've already traversed
+        // the whole hvcc structure above without issues
+        num_nalus = AV_RB16(&extradata[pos + 1]);
+        pos += 3;
+        for (j = 0; j < num_nalus; j++) {
+            int len = AV_RB16(&extradata[pos]);
+            int strpos;
+            pos += 2;
+            if (j > 0)
+                av_strlcat(psets, ",", MAX_PSET_SIZE);
+            strpos = strlen(psets);
+            if (!av_base64_encode(psets + strpos, MAX_PSET_SIZE - strpos,
+                                  &extradata[pos], len)) {
+                av_free(psets);
+                goto err;
+            }
+            pos += len;
+        }
+    }
+    av_free(tmpbuf);
 
     return psets;
+
+err:
+    av_free(tmpbuf);
+    return NULL;
 }
 
-static char *extradata2config(AVCodecContext *c)
+static char *extradata2config(AVFormatContext *s, AVCodecParameters *par)
 {
     char *config;
 
-    if (c->extradata_size > MAX_EXTRADATA_SIZE) {
-        av_log(c, AV_LOG_ERROR, "Too much extradata!\n");
+    if (par->extradata_size > MAX_EXTRADATA_SIZE) {
+        av_log(s, AV_LOG_ERROR, "Too much extradata!\n");
 
         return NULL;
     }
-    config = av_malloc(10 + c->extradata_size * 2);
+    config = av_malloc(10 + par->extradata_size * 2);
     if (!config) {
-        av_log(c, AV_LOG_ERROR, "Cannot allocate memory for the config info.\n");
+        av_log(s, AV_LOG_ERROR, "Cannot allocate memory for the config info.\n");
         return NULL;
     }
     memcpy(config, "; config=", 9);
-    ff_data_to_hex(config + 9, c->extradata, c->extradata_size, 0);
-    config[9 + c->extradata_size * 2] = 0;
+    ff_data_to_hex(config + 9, par->extradata, par->extradata_size, 0);
+    config[9 + par->extradata_size * 2] = 0;
 
     return config;
 }
 
-static char *xiph_extradata2config(AVCodecContext *c)
+static char *xiph_extradata2config(AVFormatContext *s, AVCodecParameters *par)
 {
     char *config, *encoded_config;
-    uint8_t *header_start[3];
+    const uint8_t *header_start[3];
     int headers_len, header_len[3], config_len;
     int first_header_size;
 
-    switch (c->codec_id) {
+    switch (par->codec_id) {
     case AV_CODEC_ID_THEORA:
         first_header_size = 42;
         break;
@@ -276,14 +360,14 @@ static char *xiph_extradata2config(AVCodecContext *c)
         first_header_size = 30;
         break;
     default:
-        av_log(c, AV_LOG_ERROR, "Unsupported Xiph codec ID\n");
+        av_log(s, AV_LOG_ERROR, "Unsupported Xiph codec ID\n");
         return NULL;
     }
 
-    if (avpriv_split_xiph_headers(c->extradata, c->extradata_size,
+    if (avpriv_split_xiph_headers(par->extradata, par->extradata_size,
                               first_header_size, header_start,
                               header_len) < 0) {
-        av_log(c, AV_LOG_ERROR, "Extradata corrupt.\n");
+        av_log(s, AV_LOG_ERROR, "Extradata corrupt.\n");
         return NULL;
     }
 
@@ -325,12 +409,12 @@ static char *xiph_extradata2config(AVCodecContext *c)
     return encoded_config;
 
 xiph_fail:
-    av_log(c, AV_LOG_ERROR,
+    av_log(s, AV_LOG_ERROR,
            "Not enough memory for configuration string\n");
     return NULL;
 }
 
-static int latm_context2profilelevel(AVCodecContext *c)
+static int latm_context2profilelevel(AVCodecParameters *par)
 {
     /* MP4A-LATM
      * The RTP payload format specification is described in RFC 3016
@@ -341,17 +425,17 @@ static int latm_context2profilelevel(AVCodecContext *c)
     /* TODO: AAC Profile only supports AAC LC Object Type.
      * Different Object Types should implement different Profile Levels */
 
-    if (c->sample_rate <= 24000) {
-        if (c->channels <= 2)
+    if (par->sample_rate <= 24000) {
+        if (par->channels <= 2)
             profile_level = 0x28; // AAC Profile, Level 1
-    } else if (c->sample_rate <= 48000) {
-        if (c->channels <= 2) {
+    } else if (par->sample_rate <= 48000) {
+        if (par->channels <= 2) {
             profile_level = 0x29; // AAC Profile, Level 2
-        } else if (c->channels <= 5) {
+        } else if (par->channels <= 5) {
             profile_level = 0x2A; // AAC Profile, Level 4
         }
-    } else if (c->sample_rate <= 96000) {
-        if (c->channels <= 5) {
+    } else if (par->sample_rate <= 96000) {
+        if (par->channels <= 5) {
             profile_level = 0x2B; // AAC Profile, Level 5
         }
     }
@@ -359,7 +443,7 @@ static int latm_context2profilelevel(AVCodecContext *c)
     return profile_level;
 }
 
-static char *latm_context2config(AVCodecContext *c)
+static char *latm_context2config(AVFormatContext *s, AVCodecParameters *par)
 {
     /* MP4A-LATM
      * The RTP payload format specification is described in RFC 3016
@@ -370,23 +454,23 @@ static char *latm_context2config(AVCodecContext *c)
     char *config;
 
     for (rate_index = 0; rate_index < 16; rate_index++)
-        if (avpriv_mpeg4audio_sample_rates[rate_index] == c->sample_rate)
+        if (avpriv_mpeg4audio_sample_rates[rate_index] == par->sample_rate)
             break;
     if (rate_index == 16) {
-        av_log(c, AV_LOG_ERROR, "Unsupported sample rate\n");
+        av_log(s, AV_LOG_ERROR, "Unsupported sample rate\n");
         return NULL;
     }
 
     config_byte[0] = 0x40;
     config_byte[1] = 0;
     config_byte[2] = 0x20 | rate_index;
-    config_byte[3] = c->channels << 4;
+    config_byte[3] = par->channels << 4;
     config_byte[4] = 0x3f;
     config_byte[5] = 0xc0;
 
     config = av_malloc(6*2+1);
     if (!config) {
-        av_log(c, AV_LOG_ERROR, "Cannot allocate memory for the config info.\n");
+        av_log(s, AV_LOG_ERROR, "Cannot allocate memory for the config info.\n");
         return NULL;
     }
     ff_data_to_hex(config, config_byte, 6, 1);
@@ -395,18 +479,22 @@ static char *latm_context2config(AVCodecContext *c)
     return config;
 }
 
-static char *sdp_write_media_attributes(char *buff, int size, AVCodecContext *c, int payload_type, AVFormatContext *fmt)
+static char *sdp_write_media_attributes(char *buff, int size, AVStream *st, int payload_type, AVFormatContext *fmt)
 {
     char *config = NULL;
+    AVCodecParameters *p = st->codecpar;
 
-    switch (c->codec_id) {
+    switch (p->codec_id) {
+        case AV_CODEC_ID_DIRAC:
+            av_strlcatf(buff, size, "a=rtpmap:%d VC2/90000\r\n", payload_type);
+            break;
         case AV_CODEC_ID_H264: {
             int mode = 1;
             if (fmt && fmt->oformat && fmt->oformat->priv_class &&
                 av_opt_flag_is_set(fmt->priv_data, "rtpflags", "h264_mode0"))
                 mode = 0;
-            if (c->extradata_size) {
-                config = extradata2psets(c);
+            if (p->extradata_size) {
+                config = extradata2psets(fmt, p);
             }
             av_strlcatf(buff, size, "a=rtpmap:%d H264/90000\r\n"
                                     "a=fmtp:%d packetization-mode=%d%s\r\n",
@@ -414,6 +502,20 @@ static char *sdp_write_media_attributes(char *buff, int size, AVCodecContext *c,
                                      payload_type, mode, config ? config : "");
             break;
         }
+        case AV_CODEC_ID_H261:
+        {
+            const char *pic_fmt = NULL;
+            /* only QCIF and CIF are specified as supported in RFC 4587 */
+            if (p->width == 176 && p->height == 144)
+                pic_fmt = "QCIF=1";
+            else if (p->width == 352 && p->height == 288)
+                pic_fmt = "CIF=1";
+            if (payload_type >= RTP_PT_PRIVATE)
+                av_strlcatf(buff, size, "a=rtpmap:%d H261/90000\r\n", payload_type);
+            if (pic_fmt)
+                av_strlcatf(buff, size, "a=fmtp:%d %s\r\n", payload_type, pic_fmt);
+            break;
+        }
         case AV_CODEC_ID_H263:
         case AV_CODEC_ID_H263P:
             /* a=framesize is required by 3GPP TS 26.234 (PSS). It
@@ -422,15 +524,23 @@ static char *sdp_write_media_attributes(char *buff, int size, AVCodecContext *c,
              * stagefright and on Samsung bada. */
             if (!fmt || !fmt->oformat->priv_class ||
                 !av_opt_flag_is_set(fmt->priv_data, "rtpflags", "rfc2190") ||
-                c->codec_id == AV_CODEC_ID_H263P)
+                p->codec_id == AV_CODEC_ID_H263P)
             av_strlcatf(buff, size, "a=rtpmap:%d H263-2000/90000\r\n"
                                     "a=framesize:%d %d-%d\r\n",
                                     payload_type,
-                                    payload_type, c->width, c->height);
+                                    payload_type, p->width, p->height);
+            break;
+        case AV_CODEC_ID_HEVC:
+            if (p->extradata_size)
+                config = extradata2psets_hevc(p);
+            av_strlcatf(buff, size, "a=rtpmap:%d H265/90000\r\n", payload_type);
+            if (config)
+                av_strlcatf(buff, size, "a=fmtp:%d %s\r\n",
+                                         payload_type, config);
             break;
         case AV_CODEC_ID_MPEG4:
-            if (c->extradata_size) {
-                config = extradata2config(c);
+            if (p->extradata_size) {
+                config = extradata2config(fmt, p);
             }
             av_strlcatf(buff, size, "a=rtpmap:%d MP4V-ES/90000\r\n"
                                     "a=fmtp:%d profile-level-id=1%s\r\n",
@@ -440,21 +550,21 @@ static char *sdp_write_media_attributes(char *buff, int size, AVCodecContext *c,
         case AV_CODEC_ID_AAC:
             if (fmt && fmt->oformat && fmt->oformat->priv_class &&
                 av_opt_flag_is_set(fmt->priv_data, "rtpflags", "latm")) {
-                config = latm_context2config(c);
+                config = latm_context2config(fmt, p);
                 if (!config)
                     return NULL;
                 av_strlcatf(buff, size, "a=rtpmap:%d MP4A-LATM/%d/%d\r\n"
                                         "a=fmtp:%d profile-level-id=%d;cpresent=0;config=%s\r\n",
-                                         payload_type, c->sample_rate, c->channels,
-                                         payload_type, latm_context2profilelevel(c), config);
+                                         payload_type, p->sample_rate, p->channels,
+                                         payload_type, latm_context2profilelevel(p), config);
             } else {
-                if (c->extradata_size) {
-                    config = extradata2config(c);
+                if (p->extradata_size) {
+                    config = extradata2config(fmt, p);
                 } else {
                     /* FIXME: maybe we can forge config information based on the
                      *        codec parameters...
                      */
-                    av_log(c, AV_LOG_ERROR, "AAC with no global headers is currently not supported.\n");
+                    av_log(fmt, AV_LOG_ERROR, "AAC with no global headers is currently not supported.\n");
                     return NULL;
                 }
                 if (!config) {
@@ -464,7 +574,7 @@ static char *sdp_write_media_attributes(char *buff, int size, AVCodecContext *c,
                                         "a=fmtp:%d profile-level-id=1;"
                                         "mode=AAC-hbr;sizelength=13;indexlength=3;"
                                         "indexdeltalength=3%s\r\n",
-                                         payload_type, c->sample_rate, c->channels,
+                                         payload_type, p->sample_rate, p->channels,
                                          payload_type, config);
             }
             break;
@@ -472,48 +582,48 @@ static char *sdp_write_media_attributes(char *buff, int size, AVCodecContext *c,
             if (payload_type >= RTP_PT_PRIVATE)
                 av_strlcatf(buff, size, "a=rtpmap:%d L16/%d/%d\r\n",
                                          payload_type,
-                                         c->sample_rate, c->channels);
+                                         p->sample_rate, p->channels);
             break;
         case AV_CODEC_ID_PCM_MULAW:
             if (payload_type >= RTP_PT_PRIVATE)
                 av_strlcatf(buff, size, "a=rtpmap:%d PCMU/%d/%d\r\n",
                                          payload_type,
-                                         c->sample_rate, c->channels);
+                                         p->sample_rate, p->channels);
             break;
         case AV_CODEC_ID_PCM_ALAW:
             if (payload_type >= RTP_PT_PRIVATE)
                 av_strlcatf(buff, size, "a=rtpmap:%d PCMA/%d/%d\r\n",
                                          payload_type,
-                                         c->sample_rate, c->channels);
+                                         p->sample_rate, p->channels);
             break;
         case AV_CODEC_ID_AMR_NB:
             av_strlcatf(buff, size, "a=rtpmap:%d AMR/%d/%d\r\n"
                                     "a=fmtp:%d octet-align=1\r\n",
-                                     payload_type, c->sample_rate, c->channels,
+                                     payload_type, p->sample_rate, p->channels,
                                      payload_type);
             break;
         case AV_CODEC_ID_AMR_WB:
             av_strlcatf(buff, size, "a=rtpmap:%d AMR-WB/%d/%d\r\n"
                                     "a=fmtp:%d octet-align=1\r\n",
-                                     payload_type, c->sample_rate, c->channels,
+                                     payload_type, p->sample_rate, p->channels,
                                      payload_type);
             break;
         case AV_CODEC_ID_VORBIS:
-            if (c->extradata_size)
-                config = xiph_extradata2config(c);
+            if (p->extradata_size)
+                config = xiph_extradata2config(fmt, p);
             else
-                av_log(c, AV_LOG_ERROR, "Vorbis configuration info missing\n");
+                av_log(fmt, AV_LOG_ERROR, "Vorbis configuration info missing\n");
             if (!config)
                 return NULL;
 
             av_strlcatf(buff, size, "a=rtpmap:%d vorbis/%d/%d\r\n"
                                     "a=fmtp:%d configuration=%s\r\n",
-                                    payload_type, c->sample_rate, c->channels,
+                                    payload_type, p->sample_rate, p->channels,
                                     payload_type, config);
             break;
         case AV_CODEC_ID_THEORA: {
             const char *pix_fmt;
-            switch (c->pix_fmt) {
+            switch (p->format) {
             case AV_PIX_FMT_YUV420P:
                 pix_fmt = "YCbCr-4:2:0";
                 break;
@@ -524,14 +634,14 @@ static char *sdp_write_media_attributes(char *buff, int size, AVCodecContext *c,
                 pix_fmt = "YCbCr-4:4:4";
                 break;
             default:
-                av_log(c, AV_LOG_ERROR, "Unsupported pixel format.\n");
+                av_log(fmt, AV_LOG_ERROR, "Unsupported pixel format.\n");
                 return NULL;
             }
 
-            if (c->extradata_size)
-                config = xiph_extradata2config(c);
+            if (p->extradata_size)
+                config = xiph_extradata2config(fmt, p);
             else
-                av_log(c, AV_LOG_ERROR, "Theora configuation info missing\n");
+                av_log(fmt, AV_LOG_ERROR, "Theora configuation info missing\n");
             if (!config)
                 return NULL;
 
@@ -540,7 +650,7 @@ static char *sdp_write_media_attributes(char *buff, int size, AVCodecContext *c,
                                     "width=%d; height=%d; sampling=%s; "
                                     "configuration=%s\r\n",
                                     payload_type, payload_type,
-                                    c->width, c->height, pix_fmt, config);
+                                    p->width, p->height, pix_fmt, config);
             break;
         }
         case AV_CODEC_ID_VP8:
@@ -556,32 +666,32 @@ static char *sdp_write_media_attributes(char *buff, int size, AVCodecContext *c,
             if (payload_type >= RTP_PT_PRIVATE)
                 av_strlcatf(buff, size, "a=rtpmap:%d G722/%d/%d\r\n",
                                          payload_type,
-                                         8000, c->channels);
+                                         8000, p->channels);
             break;
         case AV_CODEC_ID_ADPCM_G726: {
             if (payload_type >= RTP_PT_PRIVATE)
                 av_strlcatf(buff, size, "a=rtpmap:%d G726-%d/%d\r\n",
                                          payload_type,
-                                         c->bits_per_coded_sample*8,
-                                         c->sample_rate);
+                                         p->bits_per_coded_sample*8,
+                                         p->sample_rate);
             break;
         }
         case AV_CODEC_ID_ILBC:
             av_strlcatf(buff, size, "a=rtpmap:%d iLBC/%d\r\n"
                                     "a=fmtp:%d mode=%d\r\n",
-                                     payload_type, c->sample_rate,
-                                     payload_type, c->block_align == 38 ? 20 : 30);
+                                     payload_type, p->sample_rate,
+                                     payload_type, p->block_align == 38 ? 20 : 30);
             break;
         case AV_CODEC_ID_SPEEX:
             av_strlcatf(buff, size, "a=rtpmap:%d speex/%d\r\n",
-                                     payload_type, c->sample_rate);
-            if (c->codec) {
+                                     payload_type, p->sample_rate);
+            if (st->codec) {
                 const char *mode;
                 uint64_t vad_option;
 
-                if (c->flags & CODEC_FLAG_QSCALE)
+                if (st->codec->flags & AV_CODEC_FLAG_QSCALE)
                       mode = "on";
-                else if (!av_opt_get_int(c, "vad", AV_OPT_FLAG_ENCODING_PARAM, &vad_option) && vad_option)
+                else if (!av_opt_get_int(st->codec, "vad", AV_OPT_FLAG_ENCODING_PARAM, &vad_option) && vad_option)
                       mode = "vad";
                 else
                       mode = "off";
@@ -591,8 +701,18 @@ static char *sdp_write_media_attributes(char *buff, int size, AVCodecContext *c,
             }
             break;
         case AV_CODEC_ID_OPUS:
-            av_strlcatf(buff, size, "a=rtpmap:%d opus/48000\r\n",
+            /* The opus RTP draft says that all opus streams MUST be declared
+               as stereo, to avoid negotiation failures. The actual number of
+               channels can change on a packet-by-packet basis. The number of
+               channels a receiver prefers to receive or a sender plans to send
+               can be declared via fmtp parameters (both default to mono), but
+               receivers MUST be able to receive and process stereo packets. */
+            av_strlcatf(buff, size, "a=rtpmap:%d opus/48000/2\r\n",
                                      payload_type);
+            if (p->channels == 2) {
+                av_strlcatf(buff, size, "a=fmtp:%d sprop-stereo=1\r\n",
+                                         payload_type);
+            }
             break;
         default:
             /* Nothing special to do here... */
@@ -608,13 +728,13 @@ void ff_sdp_write_media(char *buff, int size, AVStream *st, int idx,
                         const char *dest_addr, const char *dest_type,
                         int port, int ttl, AVFormatContext *fmt)
 {
-    AVCodecContext *c = st->codec;
+    AVCodecParameters *p = st->codecpar;
     const char *type;
     int payload_type;
 
-    payload_type = ff_rtp_get_payload_type(fmt, c, idx);
+    payload_type = ff_rtp_get_payload_type(fmt, st->codecpar, idx);
 
-    switch (c->codec_type) {
+    switch (p->codec_type) {
         case AVMEDIA_TYPE_VIDEO   : type = "video"      ; break;
         case AVMEDIA_TYPE_AUDIO   : type = "audio"      ; break;
         case AVMEDIA_TYPE_SUBTITLE: type = "text"       ; break;
@@ -623,11 +743,11 @@ void ff_sdp_write_media(char *buff, int size, AVStream *st, int idx,
 
     av_strlcatf(buff, size, "m=%s %d RTP/AVP %d\r\n", type, port, payload_type);
     sdp_write_address(buff, size, dest_addr, dest_type, ttl);
-    if (c->bit_rate) {
-        av_strlcatf(buff, size, "b=AS:%d\r\n", c->bit_rate / 1000);
+    if (p->bit_rate) {
+        av_strlcatf(buff, size, "b=AS:%"PRId64"\r\n", (int64_t)p->bit_rate / 1000);
     }
 
-    sdp_write_media_attributes(buff, size, c, payload_type, fmt);
+    sdp_write_media_attributes(buff, size, st, payload_type, fmt);
 }
 
 int av_sdp_create(AVFormatContext *ac[], int n_files, char *buf, int size)