H264 编码 - 无法使用 VLC Player 播放视频

H264 Encoding - Could not play video using VLC Player

我在使用 FFmpeg libav 正确编码 H264 视频时遇到问题。我无法在 VLC 媒体播放器 中播放编码视频,虽然我可以在 MPC-HC 上播放视频,但时间显示 00:00/00:00.显然我错过了一些东西。

来自 MPC-HC 的媒体信息显示:

General
Format : AVC
Format/Info : Advanced Video Codec
File size : 110 KiB
Duration : 2s 400ms
Overall bit rate : 375 Kbps
Writing library : x264 core 148 r2665 a01e339
Encoding settings : cabac=0 / ref=3 / deblock=1:0:0 / analyse=0x1:0x111 / me=hex / subme=7 / psy=1 / psy_rd=1.00:0.00 / mixed_ref=1 / me_range=16 / chroma_me=1 / trellis=1 / 8x8dct=0 / cqm=0 / deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=-2 / threads=7 / lookahead_threads=1 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / bluray_compat=0 / constrained_intra=0 / bframes=0 / weightp=0 / keyint=12 / keyint_min=1 / scenecut=40 / intra_refresh=0 / rc_lookahead=12 / rc=abr / mbtree=1 / bitrate=2000 / ratetol=1.0 / qcomp=0.60 / qpmin=0 / qpmax=69 / qpstep=4 / ip_ratio=1.40 / aq=1:1.00

Video
Format : AVC
Format/Info : Advanced Video Codec
Format profile : Baseline@L2.1
Format settings, CABAC : No
Format settings, ReFrames : 3 frames
Format settings, GOP : M=1, N=12
Duration : 2s 400ms
Bit rate : 2 000 Kbps
Width : 320 pixels
Height : 240 pixels
Display aspect ratio : 4:3
Frame rate mode : Variable
Frame rate : 20.833 fps
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Progressive
Bits/(Pixel*Frame) : 1.250
Stream size : 586 KiB
Writing library : x264 core 148 r2665 a01e339
Encoding settings : cabac=0 / ref=3 / deblock=1:0:0 / analyse=0x1:0x111 / me=hex / subme=7 / psy=1 / psy_rd=1.00:0.00 / mixed_ref=1 / me_range=16 / chroma_me=1 / trellis=1 / 8x8dct=0 / cqm=0 / deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=-2 / threads=7 / lookahead_threads=1 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / bluray_compat=0 / constrained_intra=0 / bframes=0 / weightp=0 / keyint=12 / keyint_min=1 / scenecut=40 / intra_refresh=0 / rc_lookahead=12 / rc=abr / mbtree=1 / bitrate=2000 / ratetol=1.0 / qcomp=0.60 / qpmin=0 / qpmax=69 / qpstep=4 / ip_ratio=1.40 / aq=1:1.00

我注意到上面的信息有些奇怪: - 帧率为 20.833 fps,而不是指定的 10 fps。 - 2s 400ms 的时长似乎也不对,因为视频播放了超过 4 秒。

此外,(AVFrame* picture)->pict_type 始终设置为 AV_PICTURE_TYPE_NONE。我认为这不正常。

我使用的库是 ffmpeg-20160219-git-98a0053-win32-dev。如果您能帮助我摆脱这种困惑,我将不胜感激。

/*
 * Video encoding example
 */
char filename[] = "test.mp4";
int main(int argc, char** argv)
{
    AVCodec *codec = NULL;
    AVCodecContext *codecCtx= NULL;
    AVFormatContext *pFormatCtx = NULL;
    AVStream * pVideoStream = NULL;
    AVFrame *picture = NULL;

    int i, x, y,            //
        ret,                // Return value
        got_packet_ptr;     // Data encoded into packet

    printf("Video encoding\n");

    // Register all formats and codecs
    av_register_all();

    // allocate context
    pFormatCtx = avformat_alloc_context();
    memcpy(pFormatCtx->filename,filename,
        min(strlen(filename), sizeof(pFormatCtx->filename)));

    // guess format
    pFormatCtx->oformat = av_guess_format("h264", NULL, NULL);
    if (NULL==pFormatCtx->oformat)
    {
        cerr << "Could not guess output format" << endl;
        return -1;
    }   

    // Find the codec.
    codec = avcodec_find_encoder(pFormatCtx->oformat->video_codec);
    if (codec == NULL) {
        fprintf(stderr, "Codec not found\n");
        return -1;
    }

    // Set context
    int framerate = 10;
    codecCtx = avcodec_alloc_context3(codec);
    avcodec_get_context_defaults3(codecCtx, codec); 
    codecCtx->pix_fmt = AV_PIX_FMT_YUV420P;
    codecCtx->profile = FF_PROFILE_H264_BASELINE; 
    // Resolution must be a multiple of two.
    codecCtx->width  = 320;
    codecCtx->height = 240;

    codecCtx->bit_rate = 2000000;
    codecCtx->time_base.den = framerate;
    codecCtx->time_base.num = 1;
    codecCtx->gop_size = 12; // emit one intra frame every twelve frames at most

    // Open the codec.  
    if (avcodec_open2(codecCtx, codec, NULL) < 0) 
    {
        printf("Cannot open video codec\n");
        return -1;
    }

    // Add stream to pFormatCtx
    pVideoStream = avformat_new_stream(pFormatCtx, codec);
    if (!pVideoStream) 
    {
        printf("Cannot add new video stream\n");
        return -1;
    }
    pVideoStream->codec = codecCtx;
    pVideoStream->time_base.den = framerate;
    pVideoStream->time_base.num = 1;

    if (avio_open2(&pFormatCtx->pb, filename, AVIO_FLAG_WRITE, NULL, NULL) < 0) 
    {
        printf("Cannot open file\n");
        return -1;
    }

    // Write file header.
    avformat_write_header(pFormatCtx, NULL);

    // Create frame
    picture= av_frame_alloc();
    picture->format = codecCtx->pix_fmt;
    picture->width  = codecCtx->width;
    picture->height = codecCtx->height;

    int bufferImgSize = av_image_get_buffer_size(codecCtx->pix_fmt, codecCtx->width,
                    codecCtx->height,1);    
    av_image_alloc(picture->data, picture->linesize, codecCtx->width, codecCtx->height,                 codecCtx->pix_fmt, 32);

    AVPacket avpkt;

    /* encode 1 second of video */
    for(i=0;i<50;i++) 
    {
        /* prepare a dummy image */
        /* Y */
        for(y=0;y<codecCtx->height;y++)
        {
            for(x=0;x<codecCtx->width;x++) 
            {
                picture->data[0][y * picture->linesize[0] + x] = x + y + i * 3;
            }
        }
        /* Cb and Cr */
        for(y=0;y<codecCtx->height/2;y++) 
        {
            for(x=0;x<codecCtx->width/2;x++) 
            {
                picture->data[1][y * picture->linesize[1] + x] = 128 + y + i * 2;
                picture->data[2][y * picture->linesize[2] + x] = 64 + x + i * 5;
            }
        }

        // Get timestamp
        picture->pts = (float) i * (1000.0/(float)(codecCtx->time_base.den)) * 90; 

        // Encode frame to packet
        av_init_packet(&avpkt);
        got_packet_ptr = 0;
        int error = avcodec_encode_video2(codecCtx, &avpkt, picture, &got_packet_ptr);
        if (!error && got_packet_ptr > 0) 
        {
            // Write packet with frame.
            ret = (av_interleaved_write_frame(pFormatCtx, &avpkt) == 0);        
        }   
        av_packet_unref(&avpkt); 
    }

    // Flush remaining encoded data
    while(1)
    {
        av_init_packet(&avpkt);
        got_packet_ptr = 0;
        // Encode frame to packet.
        int error = avcodec_encode_video2(codecCtx, &avpkt, NULL, &got_packet_ptr);
        if (!error && got_packet_ptr > 0) 
        {
            // Write packet with frame.
            ret = (av_interleaved_write_frame(pFormatCtx, &avpkt) == 0);        
        } 
        else 
        {
            break;
        }
        av_packet_unref(&avpkt); 
    }
    av_write_trailer(pFormatCtx);

    av_packet_unref(&avpkt);
    av_frame_free(&picture);

    avcodec_close(codecCtx);
    av_free(codecCtx);

    cin.get();
}

从 libav 邮件列表中得到了答案(感谢 Gonzalo),我想在这里分享我的答案。

我弄乱了格式,因为 av_guess_format("h264", NULL, NULL)pFormatCtx->oformat 设置为以下内容:

pFormatCtx->oformat.name 0x009df614 "h264"
pFormatCtx->oformat.long_name 0x009df619 "raw H.264 video"
pFormatCtx->oformat.mime_type 0x00000000
pFormatCtx->oformat.extensions 0x009df629 "h264,264"
pFormatCtx->oformat.audio_codec AV_CODEC_ID_NONE
pFormatCtx->oformat.video_codec AV_CODEC_ID_H264
pFormatCtx->oformat.subtitle_codec AV_CODEC_ID_NONE
pFormatCtx->oformat.flags 128
pFormatCtx->oformat.codec_tag 0x00000000
pFormatCtx->oformat.priv_class 0x00000000 {class_name=??? item_name=??? option=??? ...}
pFormatCtx->oformat.next 0x009980c0 {name=0x009bb03e "hds" long_name=0x009bb042 "HDS Muxer" mime_type=0x00000000 ...}
pFormatCtx->oformat.priv_data_size 0
pFormatCtx->oformat.write_header 0x005bad70
pFormatCtx->oformat.write_packet 0x005bac40
pFormatCtx->oformat.write_trailer 0x00000000

更正确的调用是 av_guess_format(NULL, filename, NULL),它设置为以下内容:

pFormatCtx->oformat.name 0x009ce84c "mp4"
pFormatCtx->oformat.long_name 0x009ce850 "MP4 (MPEG-4 Part 14)"
pFormatCtx->oformat.mime_type 0x009ce689 "video/mp4"
pFormatCtx->oformat.extensions 0x009ce84c "mp4"
pFormatCtx->oformat.audio_codec AV_CODEC_ID_AAC
pFormatCtx->oformat.video_codec AV_CODEC_ID_H264
pFormatCtx->oformat.subtitle_codec AV_CODEC_ID_NONE
pFormatCtx->oformat.flags 327744
pFormatCtx->oformat.codec_tag 0x009ce868
pFormatCtx->oformat.priv_class 0x009ce880 {class_name=0x009ce870 "mp4 muxer" item_name=0x0062bc70 option=0x009cf300 ...}
pFormatCtx->oformat.next 0x0099ae00 {name=0x009d104c "mpeg" long_name=0x009d1054 "MPEG-1 Systems / MPEG program stream" mime_type=0x009d0ec8 "video/mpeg" ...}
pFormatCtx->oformat.priv_data_size 176
pFormatCtx->oformat.write_header 0x0056ad20
pFormatCtx->oformat.write_packet 0x0056a260
pFormatCtx->oformat.write_trailer 0x0056a7f0

话虽如此,如果我使用 avformat_alloc_output_context2( &pFormatCtx,NULL, NULL, filename ),生活会简单很多,因为它可以用 avformat_alloc_context()av_guess_format().

完成我需要的事情