FFmpeg RTMP推HEVC/H265流

    直播流媒体协议中，HLS和RTMP协议是两大主流协议。而众所周知的原因，RTMP在许多年前就已经停止拓展和更新，因此标准一直无法支持HEVC的编码格式。目前国内的CDN还有金山云等已经对RTMP进行了标准扩展，播放器上ijkplayer也扩展了该修改。

    具体FFmpeg的修改代码如下：

From e40fcb1113cb1c93c48b8ef74b8aec6437f23d84 Mon Sep 17 00:00:00 2001
From: Franken Zeng 
Date: Wed, 14 Jun 2017 21:33:54 +0800
Subject: [PATCH] The RTMP protocol extensions for H.265/HEVC

---
 libavformat/flv.h    |  1 +
 libavformat/flvdec.c | 16 +++++++++++++---
 libavformat/flvenc.c | 29 ++++++++++++++++++++---------
 3 files changed, 34 insertions(+), 12 deletions(-)

diff --git a/libavformat/flv.h b/libavformat/flv.h
index df5ce3d17f8..089bc76972d 100644
--- a/libavformat/flv.h
+++ b/libavformat/flv.h
@@ -109,6 +109,7 @@ enum {
     FLV_CODECID_H264    = 7,
     FLV_CODECID_REALH263= 8,
     FLV_CODECID_MPEG4   = 9,
+    FLV_CODECID_HEVC   = 12,
 };
 
 enum {
diff --git a/libavformat/flvdec.c b/libavformat/flvdec.c
index 2d89bef15f2..c8073b88a92 100644
--- a/libavformat/flvdec.c
+++ b/libavformat/flvdec.c
@@ -36,6 +36,7 @@
 #include "internal.h"
 #include "avio_internal.h"
 #include "flv.h"
+#include "hevc.h"
 
 #define VALIDATE_INDEX_TS_THRESH 2500
 
@@ -291,6 +292,8 @@ static int flv_same_video_codec(AVCodecParameters *vpar, int flags)
         return vpar->codec_id == AV_CODEC_ID_VP6A;
     case FLV_CODECID_H264:
         return vpar->codec_id == AV_CODEC_ID_H264;
+    case FLV_CODECID_HEVC:
+        return vpar->codec_id == AV_CODEC_ID_HEVC;
     default:
         return vpar->codec_tag == flv_codecid;
     }
@@ -340,6 +343,11 @@ static int flv_set_video_codec(AVFormatContext *s, AVStream *vstream,
         par->codec_id = AV_CODEC_ID_MPEG4;
         ret = 3;
         break;
+    case FLV_CODECID_HEVC:
+        par->codec_id = AV_CODEC_ID_HEVC;
+        vstream->need_parsing = AVSTREAM_PARSE_NONE;
+        ret = 3;     // not 4, reading packet type will consume one byte
+        break;
     default:
         avpriv_request_sample(s, "Video codec (%x)", flv_codecid);
         par->codec_tag = flv_codecid;
@@ -1149,10 +1157,12 @@ static int flv_read_packet(AVFormatContext *s, AVPacket *pkt)
 
     if (st->codecpar->codec_id == AV_CODEC_ID_AAC ||
         st->codecpar->codec_id == AV_CODEC_ID_H264 ||
-        st->codecpar->codec_id == AV_CODEC_ID_MPEG4) {
+        st->codecpar->codec_id == AV_CODEC_ID_MPEG4 ||
+        st->codecpar->codec_id == AV_CODEC_ID_HEVC) {
         int type = avio_r8(s->pb);
         size--;
-        if (st->codecpar->codec_id == AV_CODEC_ID_H264 || st->codecpar->codec_id == AV_CODEC_ID_MPEG4) {
+        if (st->codecpar->codec_id == AV_CODEC_ID_H264 || st->codecpar->codec_id == AV_CODEC_ID_MPEG4
+                || st->codecpar->codec_id == AV_CODEC_ID_HEVC) {
             // sign extension
             int32_t cts = (avio_rb24(s->pb) + 0xff800000) ^ 0xff800000;
             pts = dts + cts;
@@ -1168,7 +1178,7 @@ static int flv_read_packet(AVFormatContext *s, AVPacket *pkt)
             }
         }
         if (type == 0 && (!st->codecpar->extradata || st->codecpar->codec_id == AV_CODEC_ID_AAC ||
-            st->codecpar->codec_id == AV_CODEC_ID_H264)) {
+            st->codecpar->codec_id == AV_CODEC_ID_H264 || st->codecpar->codec_id == AV_CODEC_ID_HEVC)) {
             AVDictionaryEntry *t;
 
             if (st->codecpar->extradata) {
diff --git a/libavformat/flvenc.c b/libavformat/flvenc.c
index 899b07ea7be..eb955e5b451 100644
--- a/libavformat/flvenc.c
+++ b/libavformat/flvenc.c
@@ -34,6 +34,7 @@
 #include "libavutil/opt.h"
 #include "libavcodec/put_bits.h"
 #include "libavcodec/aacenctab.h"
+#include "hevc.h"
 
 
 static const AVCodecTag flv_video_codec_ids[] = {
@@ -46,6 +47,7 @@ static const AVCodecTag flv_video_codec_ids[] = {
     { AV_CODEC_ID_VP6,      FLV_CODECID_VP6 },
     { AV_CODEC_ID_VP6A,     FLV_CODECID_VP6A },
     { AV_CODEC_ID_H264,     FLV_CODECID_H264 },
+    { AV_CODEC_ID_HEVC,     FLV_CODECID_HEVC },
     { AV_CODEC_ID_NONE,     0 }
 };
 
@@ -486,7 +488,7 @@ static void flv_write_codec_header(AVFormatContext* s, AVCodecParameters* par) {
     FLVContext *flv = s->priv_data;
 
     if (par->codec_id == AV_CODEC_ID_AAC || par->codec_id == AV_CODEC_ID_H264
-            || par->codec_id == AV_CODEC_ID_MPEG4) {
+            || par->codec_id == AV_CODEC_ID_MPEG4 || par->codec_id == AV_CODEC_ID_HEVC) {
         int64_t pos;
         avio_w8(pb,
                 par->codec_type == AVMEDIA_TYPE_VIDEO ?
@@ -533,7 +535,11 @@ static void flv_write_codec_header(AVFormatContext* s, AVCodecParameters* par) {
             avio_w8(pb, par->codec_tag | FLV_FRAME_KEY); // flags
             avio_w8(pb, 0); // AVC sequence header
             avio_wb24(pb, 0); // composition time
-            ff_isom_write_avcc(pb, par->extradata, par->extradata_size);
+            if (par->codec_id == AV_CODEC_ID_HEVC) {
+                ff_isom_write_hvcc(pb, par->extradata, par->extradata_size, 0);
+            } else {
+                ff_isom_write_avcc(pb, par->extradata, par->extradata_size);
+            }
         }
         data_size = avio_tell(pb) - pos;
         avio_seek(pb, -data_size - 10, SEEK_CUR);
@@ -836,7 +842,7 @@ static int flv_write_trailer(AVFormatContext *s)
             AVCodecParameters *par = s->streams[i]->codecpar;
             FLVStreamContext *sc = s->streams[i]->priv_data;
             if (par->codec_type == AVMEDIA_TYPE_VIDEO &&
-                    (par->codec_id == AV_CODEC_ID_H264 || par->codec_id == AV_CODEC_ID_MPEG4))
+                (par->codec_id == AV_CODEC_ID_H264 || par->codec_id == AV_CODEC_ID_MPEG4 || par->codec_id == AV_CODEC_ID_HEVC))
                 put_avc_eos_tag(pb, sc->last_ts);
         }
     }
@@ -880,15 +886,16 @@ static int flv_write_packet(AVFormatContext *s, AVPacket *pkt)
     int64_t cur_offset = avio_tell(pb);
 
     if (par->codec_id == AV_CODEC_ID_VP6F || par->codec_id == AV_CODEC_ID_VP6A ||
-        par->codec_id == AV_CODEC_ID_VP6  || par->codec_id == AV_CODEC_ID_AAC)
+        par->codec_id == AV_CODEC_ID_VP6  || par->codec_id == AV_CODEC_ID_AAC) {
         flags_size = 2;
-    else if (par->codec_id == AV_CODEC_ID_H264 || par->codec_id == AV_CODEC_ID_MPEG4)
+    } else if (par->codec_id == AV_CODEC_ID_H264 || par->codec_id == AV_CODEC_ID_MPEG4 || par->codec_id == AV_CODEC_ID_HEVC) {
         flags_size = 5;
-    else
+    } else {
         flags_size = 1;
+    }
 
     if (par->codec_id == AV_CODEC_ID_AAC || par->codec_id == AV_CODEC_ID_H264
-            || par->codec_id == AV_CODEC_ID_MPEG4) {
+            || par->codec_id == AV_CODEC_ID_MPEG4 || par->codec_id == AV_CODEC_ID_HEVC) {
         int side_size = 0;
         uint8_t *side = av_packet_get_side_data(pkt, AV_PKT_DATA_NEW_EXTRADATA, &side_size);
         if (side && side_size > 0 && (side_size != par->extradata_size || memcmp(side, par->extradata, side_size))) {
@@ -951,6 +958,10 @@ static int flv_write_packet(AVFormatContext *s, AVPacket *pkt)
         if (par->extradata_size > 0 && *(uint8_t*)par->extradata != 1)
             if ((ret = ff_avc_parse_nal_units_buf(pkt->data, &data, &size)) < 0)
                 return ret;
+    } else if (par->codec_id == AV_CODEC_ID_HEVC) {
+        if (par->extradata_size > 0 && *(uint8_t*)par->extradata != 1)
+            if ((ret = ff_hevc_annexb2mp4_buf(pkt->data, &data, &size, 0, NULL)) < 0)
+                return ret;
     } else if (par->codec_id == AV_CODEC_ID_AAC && pkt->size > 2 &&
                (AV_RB16(pkt->data) & 0xfff0) == 0xfff0) {
         if (!s->streams[pkt->stream_index]->nb_frames) {
@@ -1021,9 +1032,9 @@ static int flv_write_packet(AVFormatContext *s, AVPacket *pkt)
             else
                 avio_w8(pb, ((FFALIGN(par->width,  16) - par->width) << 4) |
                              (FFALIGN(par->height, 16) - par->height));
-        } else if (par->codec_id == AV_CODEC_ID_AAC)
+        } else if (par->codec_id == AV_CODEC_ID_AAC) {
             avio_w8(pb, 1); // AAC raw
-        else if (par->codec_id == AV_CODEC_ID_H264 || par->codec_id == AV_CODEC_ID_MPEG4) {
+        } else if (par->codec_id == AV_CODEC_ID_H264 || par->codec_id == AV_CODEC_ID_MPEG4 || par->codec_id == AV_CODEC_ID_HEVC) {
             avio_w8(pb, 1); // AVC NALU
             avio_wb24(pb, pkt->pts - pkt->dts);
         }

    通过该项修改即可拓展FFmpeg中RTMP对于HEVC的支持。

    我的上一篇文章，《FFmpeg+Nginx搭建RTMP直播推流服务》记录了FFmpeg+Nginx的RTMP的搭建方式。

    但是由于服务端Nginx并没有添加HEVC下重发flv的header头部，因此播放器端只有在从流的最开始才能够成功的解码，否则会出现缺少解码参数集导致无法成功解码。解决办法有两个：

     1. 在FFmpeg代码中每一包都手动添加解码参数集于flv的header中，修改如下：

     ff_write_packet中

    if (par->codec_id == AV_CODEC_ID_AAC || par->codec_id == AV_CODEC_ID_H264
            || par->codec_id == AV_CODEC_ID_MPEG4 || par->codec_id == AV_CODEC_ID_HEVC) {
        int side_size = 0;
        uint8_t *side = av_packet_get_side_data(pkt, AV_PKT_DATA_NEW_EXTRADATA, &side_size);
        if (side && side_size > 0 && (side_size != par->extradata_size || memcmp(side, par->extradata, side_size))) {
            av_free(par->extradata);
            par->extradata = av_mallocz(side_size + AV_INPUT_BUFFER_PADDING_SIZE);
            if (!par->extradata) {
                par->extradata_size = 0;
                return AVERROR(ENOMEM);
            }
            memcpy(par->extradata, side, side_size);
            par->extradata_size = side_size;
            flv_write_codec_header(s, par, pkt->dts);
        } else {
            flv_write_codec_header(s, par, pkt->dts);
        }
    }

    2. 修改Nginx，添加HEVC的支持。这部分暂无时间修改。