ffmpeg向H264中添加SEI自定义信息的两种方式

在编解码的场景当中，经常会遇编码数据中带上自定义的内容信息，这些信息可以保存在SEI中。那么如果用FFmpeg操作简单的来说应该是什么样的呢？

下面从命令行和API使用两种方式分别来介绍一下

1. 命令行方式：

首先，使用命令行方式要先看一下对应的bitstream filter是否支持SEI的操作：

通过查看帮助信息，可以知道H264编码在ffmpeg中是可以写入SEI信息的，如果想知道其他编码是否支持这么干，那么可以先查看一下bsfs都支持哪些操作：

从图中可以看到所有的bitstream filter相关的支持，然后希望了解哪个bitstream filter的话，直接用ffmpeg -h bsf=对应的filter就可以了。

下面继续看H264的SEI操作，从帮助信息中可以看到，SEI操作的方式是通过UUID+String的方式，也就是UUID配合字符串，那么下面用命令行操作一下看看效果：

./ffmpeg -i ~/Movies/objectC/facebook.mp4 -c copy -bsf:v h264_metadata=sei_user_data=086f3693-b7b3-4f2c-9653-21492feee5b8+hello -an -t 2 -y a.h264

命令行执行后编码后生成H264内容中包含了UUID为086f3693-b7b3-4f2c-9653-21492feee5b8、字符串内容为hello的信息，下面打开a.h264文件看一下效果

从输出的文件中可以看到内容写入成功。下面看一下API的方式。

2. API方式

API方式其实与命令行方式类似，但是比命令行还要简单，下面看一下代码部分内容：

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <math.h>
 
#include <libavutil/avassert.h>
#include <libavutil/channel_layout.h>
#include <libavutil/opt.h>
#include <libavutil/mathematics.h>
#include <libavutil/timestamp.h>
#include <libavformat/avformat.h>
#include <libswscale/swscale.h>
#include <libswresample/swresample.h>
 
#define STREAM_DURATION   10.0
#define STREAM_FRAME_RATE 25 /* 25 images/s */
#define STREAM_PIX_FMT    AV_PIX_FMT_YUV420P /* default pix_fmt */
 
#define SCALE_FLAGS SWS_BICUBIC
 
// a wrapper around a single output AVStream
typedef struct OutputStream {
    AVStream *st;
    AVCodecContext *enc;
 
/* pts of the next frame that will be generated */
    int64_t next_pts;
    int samples_count;
 
    AVFrame *frame;
    AVFrame *tmp_frame;
 
    float t, tincr, tincr2;
 
    struct SwsContext *sws_ctx;
    struct SwrContext *swr_ctx;
} OutputStream;
 
static void log_packet(const AVFormatContext *fmt_ctx, const AVPacket *pkt)
{
    AVRational *time_base = &fmt_ctx->streams[pkt->stream_index]->time_base;
 
    printf("pts:%s pts_time:%s dts:%s dts_time:%s duration:%s duration_time:%s stream_index:%dn",
           av_ts2str(pkt->pts), av_ts2timestr(pkt->pts, time_base),
           av_ts2str(pkt->dts), av_ts2timestr(pkt->dts, time_base),
           av_ts2str(pkt->duration), av_ts2timestr(pkt->duration, time_base),
           pkt->stream_index);
}
 
static int write_frame(AVFormatContext *fmt_ctx, const AVRational *time_base, AVStream *st, AVPacket *pkt)
{
/* rescale output packet timestamp values from codec to stream timebase */
    av_packet_rescale_ts(pkt, *time_base, st->time_base);
    pkt->stream_index = st->index;
 
/*******代码来自 孙悟空***********/
const AVBitStreamFilter *filter;
    AVBSFContext *bsf;
    int ret = 0;
 
    filter = av_bsf_get_by_name("h264_metadata");
if (!filter) {
        printf("h264_metadata bitstream filter errorn");
return -1;
    }
    ret = av_bsf_alloc(filter, &bsf);
    av_opt_set(bsf->priv_data, "sei_user_data", "086f3693-b7b3-4f2c-9653-21492feee5b8+hello", AV_OPT_SEARCH_CHILDREN);
    ret = avcodec_parameters_copy(bsf->par_in, st->codecpar);
    ret = av_bsf_init(bsf);
    ret = avcodec_parameters_copy(st->codecpar, bsf->par_out);
    ret = av_bsf_send_packet(bsf, pkt);
while (!ret)
        ret = av_bsf_receive_packet(bsf, pkt);
    av_bsf_free(&bsf);
/*****结束。代码来自 孙悟空****/
 
/* Write the compressed frame to the media file. */
    log_packet(fmt_ctx, pkt);
return av_interleaved_write_frame(fmt_ctx, pkt);
}
 
/* Add an output stream. */
static void add_stream(OutputStream *ost, AVFormatContext *oc,
                       AVCodec **codec,
                       enum AVCodecID codec_id)
{
    AVCodecContext *c;
    int i;
 
/* find the encoder */
    *codec = avcodec_find_encoder(codec_id);
if (!(*codec)) {
        fprintf(stderr, "Could not find encoder for '%s'n",
                avcodec_get_name(codec_id));
exit(1);
    }
 
    ost->st = avformat_new_stream(oc, NULL);
if (!ost->st) {
        fprintf(stderr, "Could not allocate streamn");
exit(1);
    }
    ost->st->id = oc->nb_streams-1;
    c = avcodec_alloc_context3(*codec);
if (!c) {
        fprintf(stderr, "Could not alloc an encoding contextn");
exit(1);
    }
    ost->enc = c;
 
switch ((*codec)->type) {
case AVMEDIA_TYPE_AUDIO:
        c->sample_fmt  = (*codec)->sample_fmts ?
            (*codec)->sample_fmts[0] : AV_SAMPLE_FMT_FLTP;
        c->bit_rate    = 64000;
        c->sample_rate = 44100;
if ((*codec)->supported_samplerates) {
            c->sample_rate = (*codec)->supported_samplerates[0];
for (i = 0; (*codec)->supported_samplerates[i]; i++) {
if ((*codec)->supported_samplerates[i] == 44100)
                    c->sample_rate = 44100;
            }
        }
        c->channels        = av_get_channel_layout_nb_channels(c->channel_layout);
        c->channel_layout = AV_CH_LAYOUT_STEREO;
if ((*codec)->channel_layouts) {
            c->channel_layout = (*codec)->channel_layouts[0];
for (i = 0; (*codec)->channel_layouts[i]; i++) {
if ((*codec)->channel_layouts[i] == AV_CH_LAYOUT_STEREO)
                    c->channel_layout = AV_CH_LAYOUT_STEREO;
            }
        }
        c->channels        = av_get_channel_layout_nb_channels(c->channel_layout);
        ost->st->time_base = (AVRational){ 1, c->sample_rate };
break;
 
case AVMEDIA_TYPE_VIDEO:
        c->codec_id = codec_id;
 
        c->bit_rate = 400000;
/* Resolution must be a multiple of two. */
        c->width    = 352;
        c->height   = 288;
/* timebase: This is the fundamental unit of time (in seconds) in terms
         * of which frame timestamps are represented. For fixed-fps content,
         * timebase should be 1/framerate and timestamp increments should be
         * identical to 1. */
        ost->st->time_base = (AVRational){ 1, STREAM_FRAME_RATE };
        c->time_base       = ost->st->time_base;
 
        c->gop_size      = 12; /* emit one intra frame every twelve frames at most */
        c->pix_fmt       = STREAM_PIX_FMT;
if (c->codec_id == AV_CODEC_ID_MPEG2VIDEO) {
/* just for testing, we also add B-frames */
            c->max_b_frames = 2;
        }
if (c->codec_id == AV_CODEC_ID_MPEG1VIDEO) {
/* Needed to avoid using macroblocks in which some coeffs overflow.
             * This does not happen with normal video, it just happens here as
             * the motion of the chroma plane does not match the luma plane. */
            c->mb_decision = 2;
        }
break;
 
default:
break;
    }
 
/* Some formats want stream headers to be separate. */
if (oc->oformat->flags & AVFMT_GLOBALHEADER)
        c->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;
}
 
/**************************************************************/
/* audio output */
 
static AVFrame *alloc_audio_frame(enum AVSampleFormat sample_fmt,
                                  uint64_t channel_layout,
                                  int sample_rate, int nb_samples)
{
    AVFrame *frame = av_frame_alloc();
    int ret;
 
if (!frame) {
        fprintf(stderr, "Error allocating an audio framen");
exit(1);
    }
 
    frame->format = sample_fmt;
    frame->channel_layout = channel_layout;
    frame->sample_rate = sample_rate;
    frame->nb_samples = nb_samples;
 
if (nb_samples) {
        ret = av_frame_get_buffer(frame, 0);
if (ret < 0) {
            fprintf(stderr, "Error allocating an audio buffern");
exit(1);
        }
    }
 
return frame;
}
 
static void open_audio(AVFormatContext *oc, AVCodec *codec, OutputStream *ost, AVDictionary *opt_arg)
{
    AVCodecContext *c;
    int nb_samples;
    int ret;
    AVDictionary *opt = NULL;
 
    c = ost->enc;
 
/* open it */
    av_dict_copy(&opt, opt_arg, 0);
    ret = avcodec_open2(c, codec, &opt);
    av_dict_free(&opt);
if (ret < 0) {
        fprintf(stderr, "Could not open audio codec: %sn", av_err2str(ret));
exit(1);
    }
 
/* init signal generator */
    ost->t     = 0;
    ost->tincr = 2 * M_PI * 110.0 / c->sample_rate;
/* increment frequency by 110 Hz per second */
    ost->tincr2 = 2 * M_PI * 110.0 / c->sample_rate / c->sample_rate;
 
if (c->codec->capabilities & AV_CODEC_CAP_VARIABLE_FRAME_SIZE)
        nb_samples = 10000;
else
        nb_samples = c->frame_size;
 
    ost->frame     = alloc_audio_frame(c->sample_fmt, c->channel_layout,
                                       c->sample_rate, nb_samples);
    ost->tmp_frame = alloc_audio_frame(AV_SAMPLE_FMT_S16, c->channel_layout,
                                       c->sample_rate, nb_samples);
 
/* copy the stream parameters to the muxer */
    ret = avcodec_parameters_from_context(ost->st->codecpar, c);
if (ret < 0) {
        fprintf(stderr, "Could not copy the stream parametersn");
exit(1);
    }
 
/* create resampler context */
        ost->swr_ctx = swr_alloc();
if (!ost->swr_ctx) {
            fprintf(stderr, "Could not allocate resampler contextn");
exit(1);
        }
 
/* set options */
        av_opt_set_int       (ost->swr_ctx, "in_channel_count",   c->channels,       0);
        av_opt_set_int       (ost->swr_ctx, "in_sample_rate",     c->sample_rate,    0);
        av_opt_set_sample_fmt(ost->swr_ctx, "in_sample_fmt",      AV_SAMPLE_FMT_S16, 0);
        av_opt_set_int       (ost->swr_ctx, "out_channel_count",  c->channels,       0);
        av_opt_set_int       (ost->swr_ctx, "out_sample_rate",    c->sample_rate,    0);
        av_opt_set_sample_fmt(ost->swr_ctx, "out_sample_fmt",     c->sample_fmt,     0);
 
/* initialize the resampling context */
if ((ret = swr_init(ost->swr_ctx)) < 0) {
            fprintf(stderr, "Failed to initialize the resampling contextn");
exit(1);
        }
}
 
/* Prepare a 16 bit dummy audio frame of 'frame_size' samples and
 * 'nb_channels' channels. */
static AVFrame *get_audio_frame(OutputStream *ost)
{
    AVFrame *frame = ost->tmp_frame;
    int j, i, v;
    int16_t *q = (int16_t*)frame->data[0];
 
/* check if we want to generate more frames */
if (av_compare_ts(ost->next_pts, ost->enc->time_base,
                      STREAM_DURATION, (AVRational){ 1, 1 }) >= 0)
return NULL;
 
for (j = 0; j <frame->nb_samples; j++) {
        v = (int)(sin(ost->t) * 10000);
for (i = 0; i < ost->enc->channels; i++)
            *q++ = v;
        ost->t     += ost->tincr;
        ost->tincr += ost->tincr2;
    }
 
    frame->pts = ost->next_pts;
    ost->next_pts  += frame->nb_samples;
 
return frame;
}
 
/*
 * encode one audio frame and send it to the muxer
 * return 1 when encoding is finished, 0 otherwise
 */
static int write_audio_frame(AVFormatContext *oc, OutputStream *ost)
{
    AVCodecContext *c;
    AVPacket pkt = { 0 }; // data and size must be 0;
    AVFrame *frame;
    int ret;
    int got_packet;
    int dst_nb_samples;
 
    av_init_packet(&pkt);
    c = ost->enc;
 
    frame = get_audio_frame(ost);
 
if (frame) {
/* convert samples from native format to destination codec format, using the resampler */
/* compute destination number of samples */
            dst_nb_samples = av_rescale_rnd(swr_get_delay(ost->swr_ctx, c->sample_rate) + frame->nb_samples,
                                            c->sample_rate, c->sample_rate, AV_ROUND_UP);
            av_assert0(dst_nb_samples == frame->nb_samples);
 
/* when we pass a frame to the encoder, it may keep a reference to it
         * internally;
         * make sure we do not overwrite it here
         */
        ret = av_frame_make_writable(ost->frame);
if (ret < 0)
exit(1);
 
/* convert to destination format */
        ret = swr_convert(ost->swr_ctx,
                          ost->frame->data, dst_nb_samples,
                          (const uint8_t **)frame->data, frame->nb_samples);
if (ret < 0) {
            fprintf(stderr, "Error while convertingn");
exit(1);
        }
        frame = ost->frame;
 
        frame->pts = av_rescale_q(ost->samples_count, (AVRational){1, c->sample_rate}, c->time_base);
        ost->samples_count += dst_nb_samples;
    }
 
    ret = avcodec_encode_audio2(c, &pkt, frame, &got_packet);
if (ret < 0) {
        fprintf(stderr, "Error encoding audio frame: %sn", av_err2str(ret));
exit(1);
    }
 
if (got_packet) {
        ret = write_frame(oc, &c->time_base, ost->st, &pkt);
if (ret < 0) {
            fprintf(stderr, "Error while writing audio frame: %sn",
                    av_err2str(ret));
exit(1);
        }
    }
 
return (frame || got_packet) ? 0 : 1;
}
 
/**************************************************************/
/* video output */
 
static AVFrame *alloc_picture(enum AVPixelFormat pix_fmt, int width, int height)
{
    AVFrame *picture;
    int ret;
 
    picture = av_frame_alloc();
if (!picture)
return NULL;
 
    picture->format = pix_fmt;
    picture->width  = width;
    picture->height = height;
 
/* allocate the buffers for the frame data */
    ret = av_frame_get_buffer(picture, 32);
if (ret < 0) {
        fprintf(stderr, "Could not allocate frame data.n");
exit(1);
    }
 
return picture;
}
 
static void open_video(AVFormatContext *oc, AVCodec *codec, OutputStream *ost, AVDictionary *opt_arg)
{
    int ret;
    AVCodecContext *c = ost->enc;
    AVDictionary *opt = NULL;
 
    av_dict_copy(&opt, opt_arg, 0);
 
/* open the codec */
    ret = avcodec_open2(c, codec, &opt);
    av_dict_free(&opt);
if (ret < 0) {
        fprintf(stderr, "Could not open video codec: %sn", av_err2str(ret));
exit(1);
    }
 
/* allocate and init a re-usable frame */
    ost->frame = alloc_picture(c->pix_fmt, c->width, c->height);
if (!ost->frame) {
        fprintf(stderr, "Could not allocate video framen");
exit(1);
    }
 
/* If the output format is not YUV420P, then a temporary YUV420P
     * picture is needed too. It is then converted to the required
     * output format. */
    ost->tmp_frame = NULL;
if (c->pix_fmt != AV_PIX_FMT_YUV420P) {
        ost->tmp_frame = alloc_picture(AV_PIX_FMT_YUV420P, c->width, c->height);
if (!ost->tmp_frame) {
            fprintf(stderr, "Could not allocate temporary picturen");
exit(1);
        }
    }
 
/* copy the stream parameters to the muxer */
    ret = avcodec_parameters_from_context(ost->st->codecpar, c);
if (ret < 0) {
        fprintf(stderr, "Could not copy the stream parametersn");
exit(1);
    }
}
 
/* Prepare a dummy image. */
static void fill_yuv_image(AVFrame *pict, int frame_index,
                           int width, int height)
{
    int x, y, i;
 
    i = frame_index;
 
/* Y */
for (y = 0; y < height; y++)
for (x = 0; x < width; x++)
            pict->data[0][y * pict->linesize[0] + x] = x + y + i * 3;
 
/* Cb and Cr */
for (y = 0; y < height / 2; y++) {
for (x = 0; x < width / 2; x++) {
            pict->data[1][y * pict->linesize[1] + x] = 128 + y + i * 2;
            pict->data[2][y * pict->linesize[2] + x] = 64 + x + i * 5;
        }
    }
}
 
static AVFrame *get_video_frame(OutputStream *ost)
{
    AVCodecContext *c = ost->enc;
 
/* check if we want to generate more frames */
if (av_compare_ts(ost->next_pts, c->time_base,
                      STREAM_DURATION, (AVRational){ 1, 1 }) >= 0)
return NULL;
 
/* when we pass a frame to the encoder, it may keep a reference to it
     * internally; make sure we do not overwrite it here */
if (av_frame_make_writable(ost->frame) < 0)
exit(1);
 
if (c->pix_fmt != AV_PIX_FMT_YUV420P) {
/* as we only generate a YUV420P picture, we must convert it
         * to the codec pixel format if needed */
if (!ost->sws_ctx) {
            ost->sws_ctx = sws_getContext(c->width, c->height,
                                          AV_PIX_FMT_YUV420P,
                                          c->width, c->height,
                                          c->pix_fmt,
                                          SCALE_FLAGS, NULL, NULL, NULL);
if (!ost->sws_ctx) {
                fprintf(stderr,
"Could not initialize the conversion contextn");
exit(1);
            }
        }
        fill_yuv_image(ost->tmp_frame, ost->next_pts, c->width, c->height);
        sws_scale(ost->sws_ctx, (const uint8_t * const *) ost->tmp_frame->data,
                  ost->tmp_frame->linesize, 0, c->height, ost->frame->data,
                  ost->frame->linesize);
    } else {
        fill_yuv_image(ost->frame, ost->next_pts, c->width, c->height);
    }
 
    ost->frame->pts = ost->next_pts++;
 
return ost->frame;
}
 
/*
 * encode one video frame and send it to the muxer
 * return 1 when encoding is finished, 0 otherwise
 */
static int write_video_frame(AVFormatContext *oc, OutputStream *ost)
{
    int ret;
    AVCodecContext *c;
    AVFrame *frame;
    int got_packet = 0;
    AVPacket pkt = { 0 };
 
    c = ost->enc;
 
    frame = get_video_frame(ost);
 
    av_init_packet(&pkt);
 
/* encode the image */
    ret = avcodec_encode_video2(c, &pkt, frame, &got_packet);
if (ret < 0) {
        fprintf(stderr, "Error encoding video frame: %sn", av_err2str(ret));
exit(1);
    }
 
if (got_packet) {
        ret = write_frame(oc, &c->time_base, ost->st, &pkt);
    } else {
        ret = 0;
    }
 
if (ret < 0) {
        fprintf(stderr, "Error while writing video frame: %sn", av_err2str(ret));
exit(1);
    }
 
return (frame || got_packet) ? 0 : 1;
}
 
static void close_stream(AVFormatContext *oc, OutputStream *ost)
{
    avcodec_free_context(&ost->enc);
    av_frame_free(&ost->frame);
    av_frame_free(&ost->tmp_frame);
    sws_freeContext(ost->sws_ctx);
    swr_free(&ost->swr_ctx);
}
 
/**************************************************************/
/* media file output */
 
int main(int argc, char **argv)
{
    OutputStream video_st = { 0 }, audio_st = { 0 };
const char *filename;
    AVOutputFormat *fmt;
    AVFormatContext *oc;
    AVCodec *audio_codec, *video_codec;
    int ret;
    int have_video = 0, have_audio = 0;
    int encode_video = 0, encode_audio = 0;
    AVDictionary *opt = NULL;
    int i;
 
if (argc < 2) {
        printf("usage: %s output_filen"
"API example program to output a media file with libavformat.n"
"This program generates a synthetic audio and video stream, encodes andn"
"muxes them into a file named output_file.n"
"The output format is automatically guessed according to the file extension.n"
"Raw images can also be output by using '%%d' in the filename.n"
"n", argv[0]);
return 1;
    }
 
    filename = argv[1];
for (i = 2; i+1 < argc; i+=2) {
if (!strcmp(argv[i], "-flags") || !strcmp(argv[i], "-fflags"))
            av_dict_set(&opt, argv[i]+1, argv[i+1], 0);
    }
 
/* allocate the output media context */
    avformat_alloc_output_context2(&oc, NULL, NULL, filename);
if (!oc) {
        printf("Could not deduce output format from file extension: using MPEG.n");
        avformat_alloc_output_context2(&oc, NULL, "mpeg", filename);
    }
if (!oc)
return 1;
 
    fmt = oc->oformat;
 
/* Add the audio and video streams using the default format codecs
     * and initialize the codecs. */
if (fmt->video_codec != AV_CODEC_ID_NONE) {
        add_stream(&video_st, oc, &video_codec, fmt->video_codec);
        have_video = 1;
        encode_video = 1;
    }
if (fmt->audio_codec != AV_CODEC_ID_NONE) {
        add_stream(&audio_st, oc, &audio_codec, fmt->audio_codec);
        have_audio = 1;
        encode_audio = 1;
    }
 
/* Now that all the parameters are set, we can open the audio and
     * video codecs and allocate the necessary encode buffers. */
if (have_video)
        open_video(oc, video_codec, &video_st, opt);
 
if (have_audio)
        open_audio(oc, audio_codec, &audio_st, opt);
 
    av_dump_format(oc, 0, filename, 1);
 
/* open the output file, if needed */
if (!(fmt->flags & AVFMT_NOFILE)) {
        ret = avio_open(&oc->pb, filename, AVIO_FLAG_WRITE);
if (ret < 0) {
            fprintf(stderr, "Could not open '%s': %sn", filename,
                    av_err2str(ret));
return 1;
        }
    }
 
/* Write the stream header, if any. */
    ret = avformat_write_header(oc, &opt);
if (ret < 0) {
        fprintf(stderr, "Error occurred when opening output file: %sn",
                av_err2str(ret));
return 1;
    }
 
while (encode_video || encode_audio) {
/* select the stream to encode */
if (encode_video &&
            (!encode_audio || av_compare_ts(video_st.next_pts, video_st.enc->time_base,
                                            audio_st.next_pts, audio_st.enc->time_base) <= 0)) {
            encode_video = !write_video_frame(oc, &video_st);
        } else {
            encode_audio = !write_audio_frame(oc, &audio_st);
        }
    }
 
/* Write the trailer, if any. The trailer must be written before you
     * close the CodecContexts open when you wrote the header; otherwise
     * av_write_trailer() may try to use memory that was freed on
     * av_codec_close(). */
    av_write_trailer(oc);
 
/* Close each codec. */
if (have_video)
        close_stream(oc, &video_st);
if (have_audio)
        close_stream(oc, &audio_st);
 
if (!(fmt->flags & AVFMT_NOFILE))
/* Close the output file. */
        avio_closep(&oc->pb);
 
/* free the stream */
    avformat_free_context(oc);
 
return 0;
}
bogon:xxx StevenLiu$

av_opt_set(bsf->priv_data, "sei_user_data", "086f3693-b7b3-4f2c-9653-21492feee5b8+hello", AV_OPT_SEARCH_CHILDREN);

关键是这句，然后编译之后执行之后效果与命令行输出的效果图是一样的。

到这里，添加sei信息到h264中就可以搞定了。

作者：悟空；公众号：流媒体技术