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  • H.264 muxing to MP4 from CCTV (HW) encoder using ffmpeg library in C / C++, how to fetch AVCodecContext::extradata

    26 mai 2016, par Dom

    I am trying to mux a video to mp4 file from packets received via SDK API of CCTV camera. The stream from CCTV seems to consist of packets of h264 I and P-frames only (no B-frames).

    The problem is, that the file is not playable in Daum PotPlayer when I leave the AVCodecContext::extradata empty, however, I can play the file in VLC. If I feed the extra data (probably not correctly - I just copy the first 50 bytes from the packet received from the HW encoder), the file is playable in PotPlayer, but not in VLC.

    I do not know, how to prepare the extradata properly.

    The code below shows the muxing.

    void WriteVideo()
    
{
    
    AVFormatContext* formatContext = nullptr;
    
    AVStream* stream = nullptr;
    

    
    int ret = 0;
    

    
    ret = avformat_alloc_output_context2(&formatContext, nullptr, "mp4", OUTPUT_V_FILE_NAME);
    
    if (ret < 0)
    
    {
    
        fprintf(stderr, "Error occurred when allocating output context: %d\n", ret);
    
        return;
    
    }
    

    
    stream = avformat_new_stream(formatContext, nullptr);
    
    if (!stream)
    
    {
    
        avformat_free_context(formatContext);
    
        formatContext = nullptr;
    
        fprintf(stderr, "Error occurred creating new stream");
    
        return;
    
    }
    

    
    stream->codec->codec_tag = 0;
    

    
    if (formatContext->oformat->flags & AVFMT_GLOBALHEADER)
    
    {
    
        stream->codec->flags |= CODEC_FLAG_GLOBAL_HEADER;
    
    }
    

    

    
    stream->codec->codec_type = AVMEDIA_TYPE_VIDEO;
    
    stream->codec->codec_id = AV_CODEC_ID_H264;
    
    stream->codec->pix_fmt = AV_PIX_FMT_YUV420P;
    
    stream->codec->bit_rate = 4096000; // 8192000; // 4096000; // 384000;
    
    stream->codec->width = 1920; // 352
    
    stream->codec->height = 1080; // 288
    
    stream->codec->gop_size = 50;
    

    
    AVRational tb;
    
    tb.num = 1;
    
    tb.den = 25;
    
    stream->codec->time_base = tb;
    
    //stream->codec->field_order = AVFieldOrder::AV_FIELD_UNKNOWN;
    
    //stream->codec->color_primaries = AVColorPrimaries::AVCOL_PRI_BT470BG;
    
    //stream->codec->color_trc = AVColorTransferCharacteristic::AVCOL_TRC_GAMMA22;
    
    //stream->codec->colorspace = AVColorSpace::AVCOL_SPC_BT470BG;
    
    //stream->codec->chroma_sample_location = AVChromaLocation::AVCHROMA_LOC_CENTER;
    
    AVRational aratio;
    
    aratio.num = 1;
    
    aratio.den = 1;
    
    stream->codec->sample_aspect_ratio = aratio;
    
    // stream->codec->delay = 0;
    
    // stream->codec->color_range = AVColorRange::AVCOL_RANGE_MPEG;
    

    
    av_dump_format(formatContext, 0, formatContext->filename, 1);
    

    
    if (!(formatContext->oformat->flags & AVFMT_NOFILE))
    
    {
    
        if (avio_open(&formatContext->pb, formatContext->filename, AVIO_FLAG_WRITE) < 0)
    
        {
    
            avformat_free_context(formatContext);
    
            formatContext = nullptr;
    
            fprintf(stderr, "Error occurred when opening output file.");
    
            return;
    

    
        }
    
    }
    

    
    avformat_write_header(formatContext, nullptr);
    

    
    int frameIdx = 0;
    
    int pts = 0;
    
    int dts = 0;
    
    int pkt_pos = 0;
    
    int size = static_cast<int>(tmpRawFrameBuffer.size());
    

    
    AVPacket pkt = { 0 };
    
    av_init_packet(&amp;pkt);
    

    
    while (frameIdx &lt; size)
    
    {
    
        pkt.data = tmpRawFrameBuffer[frameIdx];
    
        pkt.size = tmpRawFrameSizes[frameIdx];
    

    
        // debug purphose start
    
        FILE* f;
    
        char filename[MAX_PATH];
    
        sprintf_s(filename, MAX_PATH, OUTPUT_PACKET_FILE_PATTERN_NAME, frameIdx);
    
        auto err = fopen_s(&amp;f, filename, "wb");
    
        if (err != 0)
    
        {
    
            fprintf(stderr, "Could not open %s\n", OUTPUT_V_FILE_NAME);
    
            exit(1);
    
        }
    

    
        fflush(stdout);
    
        fwrite(pkt.data, 1, pkt.size, f);
    
        fclose(f);
    
        // debug purphose end
    

    
        if (tmpRawFrameTypes[frameIdx] == VIDEO_I_FRAME)
    
        {
    
            pkt.flags |= AV_PKT_FLAG_KEY;
    
            stream->codec->extradata_size = 50;
    
            stream->codec->extradata = (uint8_t*)av_malloc(stream->codec->extradata_size);
    
            memcpy(stream->codec->extradata, pkt.data, stream->codec->extradata_size);
    
        }
    
        pkt.pts = pts++;
    
        pkt.dts = dts++;
    
        /* rescale output packet timestamp values from codec to stream timebase */
    
        // av_packet_rescale_ts(&amp;pkt, stream->codec->time_base, stream->time_base);
    
        pkt.pts = av_rescale_q(pkt.pts, stream->codec->time_base, stream->time_base);
    
        pkt.dts = av_rescale_q(pkt.dts, stream->codec->time_base, stream->time_base);
    
        pkt.duration = 512; // should be calculated (derived from FPS 25, and 12800)
    
        pkt.pos = -1;
    
        pkt.stream_index = stream->index;
    

    
        auto ret = av_write_frame(formatContext, &amp;pkt);
    
        if (ret &lt; 0)
    
        {
    
            fprintf(stderr, "Error while writing video frame: %d\n", ret);
    
            break;
    
        }
    
        av_packet_unref(&amp;pkt);
    
        ++frameIdx;
    
    }
    

    
    if (formatContext)
    
    {
    
        av_write_trailer(formatContext);
    
        if (!(formatContext->oformat->flags &amp; AVFMT_NOFILE)) avio_close(formatContext->pb); // close the output file
    
        avformat_free_context(formatContext);
    
        formatContext = nullptr;
    
    }
    
}
    
</int>

    It seems, the packet from camera (buffered in tmpRawFrameBuffer vector) contains some headers, but I am not able to parse them, I do not understand the meaning of the header.

    The first bytes of the I-frame packet looks like the dump bellow :

    00 00 01 FC 02 19 F0 87 A0 23 73 41 B6 C0 01 00
    
00 00 00 01 67 4D 00 2A 95 A8 1E 00 89 F9 61 00
    
00 03 00 01 00 00 03 00 32 84 00 00 00 01 68 EE 
    
3C 80 00 00 00 01 06 E5 01 19 80 00 00 00 01 65 
    
B8 00 00 08 C7 B0 23 FF F7 80 EE FE 63 B6 FB F5
    
...

    The first bytes of the first P-frame :

    00 00 01 FD E5 24 00 00 00 00 00 01 61 E0 22 27 
    
FF D6 B0 D7 A4 2B 71 6B 19 C5 87 CA BB 8B BF 60 
    
14 59 B4 00 CC BC 0F C0 9E FD 84 B5 FB C4 83 DB 
    
5A 8B 80 FC EC D6 33 6D DE 10 96 6F 31 41 86 5C 
    
D4 22 F9 33 48 5B CE 77 38 17 0C D6 DD C7 6C E8
    
...

    first bytes of next P-frame :

    00 00 01 FD 5E 2F 00 00 00 00 00 01 61 E0 42 2F 
    
FF E7 06 DD 3C 66 26 15 94 93 7A F1 30 8A 6D B8 
    
AD DD 6B 0F 38 89 1D 1B 5C AC 44 6A D7 D1 21 3B 
    
E2 29 F8 14 BB 98 1C 06 4D B6 10 BB DB B9 CA 4F 
    
0B ED B1 A9 06 78 8C EC 06 6D 9F 4F 79 0C 35 5B
    
...

    ...

    begining of next I-frame :

    00 00 01 FC 02 19 F0 87 A2 23 73 41 75 89 01 00 
    
00 00 00 01 67 4D 00 2A 95 A8 1E 00 89 F9 61 00 
    
00 03 00 01 00 00 03 00 32 84 00 00 00 01 68 EE 
    
3C 80 00 00 00 01 06 E5 01 1B 80 00 00 00 01 65 
    
B8 00 00 0F 07 F0 7F F6 6C 69 43 0F F0 28 DF 97
    
...

    Does anybody know, how to fill correctly the extradata ? I just made a copy of first 50 bytes, but it seems, this is not correct.

    Probably the headers are (AUD)(SPS)(PPS)(I-Slice)(PPS)(P-Slice)(PPS)(P-Slice) ... (AUD)(SPS)(PPS)(I-Slice) (http://stackoverflow.com/a/20686267/1699328), however, I do not know, how to extract data for the

    stream->codec->extradata

    I tried to get some inspiration in this post H.264 muxed to MP4 using libavformat not playing back, but I am not able to figure out what are values of spsFrameLen, ppsFrameLen and spsFrame.

    The result of the muxer (first and last bytes of the mp4 file) :

    00 00 00 20 66 74 79 70 69 73 6F 6D 00 00 02 00 
    
69 73 6F 6D 69 73 6F 32 61 76 63 31 6D 70 34 31 
    
00 00 00 08 66 72 65 65 00 26 2E 6D 6D 64 61 74 
    
00 00 00 0D FC 02 19 F0 87 A0 23 73 41 B6 C0 01 
    
00 00 00 00 16 67 4D 00 2A 95 A8 1E 00 89 F9 61 
    
00 00 03 00 01 00 00 03 00 32 84 00 00 00 04 68 
    
EE 3C 80 00 00 00 05 06 E5 01 19 80 00 01 C0 87 
    
65 B8 00 00 08 C7 B0 23 FF F7 80 EE FE 63 B6 FB 
    
F5 97 A8 6B 48 39 61 99 FD 99 27 41 F2 78 54 EE 
    
D1 38 8E E8 18 DD 05 E4 BA F4 EB 69 CF 91 5C 34
    
...
    
...
    
...
    
95 B8 D8 D4 C3 AF A1 BA AC 28 F0 D4 D4 7C 48 9A 
    
0C A6 8C 4C 98 00 00 05 1E 6D 6F 6F 76 00 00 00 
    
6C 6D 76 68 64 00 00 00 00 00 00 00 00 00 00 00 
    
00 00 00 03 E8 00 00 13 B0 00 01 00 00 01 00 00 
    
00 00 00 00 00 00 00 00 00 00 01 00 00 00 00 00 
    
00 00 00 00 00 00 00 00 00 00 01 00 00 00 00 00 
    
00 00 00 00 00 00 00 00 00 40 00 00 00 00 00 00 
    
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
    
00 00 00 00 00 00 00 00 02 00 00 04 48 74 72 61 
    
6B 00 00 00 5C 74 6B 68 64 00 00 00 03 00 00 00 
    
00 00 00 00 00 00 00 00 01 00 00 00 00 00 00 13 
    
B0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
    
00 00 01 00 00 00 00 00 00 00 00 00 00 00 00 00 
    
00 00 01 00 00 00 00 00 00 00 00 00 00 00 00 00 
    
00 40 00 00 00 07 80 00 00 04 38 00 00 00 00 00 
    
24 65 64 74 73 00 00 00 1C 65 6C 73 74 00 00 00 
    
00 00 00 00 01 00 00 13 B0 00 00 00 00 00 01 00 
    
00 00 00 03 C0 6D 64 69 61 00 00 00 20 6D 64 68 
    
64 00 00 00 00 00 00 00 00 00 00 00 00 00 00 32 
    
00 00 00 FC 00 55 C4 00 00 00 00 00 2D 68 64 6C 
    
72 00 00 00 00 00 00 00 00 76 69 64 65 00 00 00 
    
00 00 00 00 00 00 00 00 00 56 69 64 65 6F 48 61 
    
6E 64 6C 65 72 00 00 00 03 6B 6D 69 6E 66 00 00 
    
00 14 76 6D 68 64 00 00 00 01 00 00 00 00 00 00 
    
00 00 00 00 00 24 64 69 6E 66 00 00 00 1C 64 72 
    
65 66 00 00 00 00 00 00 00 01 00 00 00 0C 75 72 
    
6C 20 00 00 00 01 00 00 03 2B 73 74 62 6C 00 00 
    
00 93 73 74 73 64 00 00 00 00 00 00 00 01 00 00 
    
00 83 61 76 63 31 00 00 00 00 00 00 00 01 00 00 
    
00 00 00 00 00 00 00 00 00 00 00 00 00 00 07 80 
    
04 38 00 48 00 00 00 48 00 00 00 00 00 00 00 01 
    
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
    
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
    
00 18 FF FF 00 00 00 2D 61 76 63 43 01 4D 00 2A 
    
FF E1 00 16 67 4D 00 2A 95 A8 1E 00 89 F9 61 00 
    
00 03 00 01 00 00 03 00 32 84 01 00 04 68 EE 3C 
    
80 00 00 00 18 73 74 74 73 00 00 00 00 00 00 00 
    
01 00 00 00 7E 00 00 02 00 00 00 00 1C 73 74 73 
    
73 00 00 00 00 00 00 00 03 00 00 00 01 00 00 00 
    
33 00 00 00 65 00 00 00 34 73 74 73 63 00 00 00 
    
00 00 00 00 03 00 00 00 01 00 00 00 3B 00 00 00 
    
01 00 00 00 02 00 00 00 37 00 00 00 01 00 00 00 
    
03 00 00 00 0C 00 00 00 01 00 00 02 0C 73 74 73 
    
7A 00 00 00 00 00 00 00 00 00 00 00 7E 00 01 C0 
    
C7 00 00 24 EE 00 00 2F 67 00 00 1D 83 00 00 2E 
    
8F 00 00 30 B6 00 00 2F 44 00 00 2F 50 00 00 34 
    
6B 00 00 30 BE 00 00 31 0C 00 00 31 E7 00 00 30 
    
EA 00 00 31 4E 00 00 31 A8 00 00 32 21 00 00 31 
    
E6 00 00 31 B5 00 00 31 14 00 00 31 AF 00 00 31 
    
9D 00 00 33 60 00 00 32 11 00 00 32 4C 00 00 31 
    
F0 00 00 32 91 00 00 43 43 00 00 44 29 00 00 44 
    
EC 00 00 44 20 00 00 44 86 00 00 45 AD 00 00 47 
    
47 00 00 46 9F 00 00 46 D9 00 00 47 BE 00 00 48 
    
CD 00 00 3E 50 00 00 40 98 00 00 41 0E 00 00 40 
    
43 00 00 41 07 00 00 41 BB 00 00 41 FF 00 00 30 
    
5E 00 00 33 C7 00 00 34 B7 00 00 33 F1 00 00 33 
    
0D 00 00 32 DB 00 01 89 86 00 00 3B E1 00 00 3C 
    
55 00 00 3C 64 00 00 3C B7 00 00 3C FD 00 00 3E 
    
54 00 00 3E C5 00 00 3E 1C 00 00 3E 94 00 00 3E 
    
44 00 00 3E D7 00 00 3F CC 00 00 3E D6 00 00 40 
    
00 00 00 40 4D 00 00 40 04 00 00 3F A9 00 00 40 
    
82 00 00 41 0F 00 00 41 64 00 00 41 E5 00 00 42 
    
1E 00 00 42 2C 00 00 42 80 00 00 42 4D 00 00 43 
    
9F 00 00 43 DA 00 00 44 45 00 00 44 21 00 00 44 
    
B7 00 00 45 22 00 00 45 E3 00 00 45 BF 00 00 46 
    
18 00 00 47 4B 00 00 45 05 00 00 47 34 00 00 46 
    
60 00 00 46 97 00 00 46 66 00 00 46 29 00 00 46 
    
38 00 00 47 1D 00 00 47 42 00 00 47 18 00 00 47 
    
13 00 00 46 52 00 00 47 48 00 00 46 F8 00 01 BE 
    
E3 00 00 3F 56 00 00 3B 32 00 00 38 F8 00 00 37 
    
56 00 00 36 2D 00 00 35 DA 00 00 34 6B 00 00 3E 
    
BE 00 00 3E B5 00 00 3F 33 00 00 3F AC 00 00 3F 
    
38 00 00 42 32 00 01 1B DC 00 01 80 50 00 01 14 
    
06 00 00 C2 BB 00 00 96 12 00 00 6D EC 00 00 54 
    
E6 00 00 3A AC 00 00 32 00 00 00 2F 0A 00 00 2D 
    
F1 00 00 1B 7F 00 00 00 1C 73 74 63 6F 00 00 00 
    
00 00 00 00 03 00 00 00 30 00 0F DD AB 00 1F 7D 
    
9E 00 00 00 62 75 64 74 61 00 00 00 5A 6D 65 74 
    
61 00 00 00 00 00 00 00 21 68 64 6C 72 00 00 00 
    
00 00 00 00 00 6D 64 69 72 61 70 70 6C 00 00 00 
    
00 00 00 00 00 00 00 00 00 2D 69 6C 73 74 00 00 
    
00 25 A9 74 6F 6F 00 00 00 1D 64 61 74 61 00 00 
    
00 01 00 00 00 00 4C 61 76 66 35 37 2E 32 33 2E 
    
31 30 30

    Thanks a lot for any advices.

  • Extract subtitle by language code via ffmpeg

    7 mai 2023, par TrustFound

    I have a simple task - extract subtitle for exact language from tvshows.&#xA;For example, I want to extract English subtitles from Netflix's show.&#xA;As you know there're a few different types of subtitles : forced, full and SDH.&#xA;So I want to extract all of them if it has eng language code.

    &#xA;

    To extract 1 subtitle from file I used this code for windows :

    &#xA;

    FOR %%i IN (*.mkv) DO (ffmpeg.exe -i "%%i" -map 0:s:m:language:eng -c copy "%%~ni".eng.srt)&#xA;

    &#xA;

    It worked fine with 1 english subtitle per file. But if it contains 2, ffmpeg shows error

    &#xA;

    &#xA;

    SRT supports only a single subtitles stream

    &#xA;

    &#xA;

    &#xA;

    MI is...

    &#xA;

      &#xA;
    • Stream #0:2(eng) : Subtitle : subrip

      • &#xA;

    • Stream #0:3(eng) : Subtitle : subrip

      • &#xA;

    • Stream #0:4(ara) : Subtitle : subrip

      • &#xA;

    • ...

      • &#xA;

    &#xA;

    &#xA;

    So I should set 2 or more output files. I tried to figure out how to do this and found similar threads on reddit and stacksoverflow. They said there's no way to do this without ffprobe.&#xA;So I used ffprobe to parse all subtitle tracks and their language code.

    &#xA;

    FOR %%i IN (*.mkv) DO (ffprobe -loglevel error -select_streams s -show_entries stream=index:stream_tags=language -of csv=p=0 -i %%i > subs.txt)&#xA;

    &#xA;

    File contains this info :

    &#xA;

      &#xA;
    • 2,eng

      • &#xA;

    • 3,eng

      • &#xA;

    • 4,ara

      • &#xA;

    • ...

      • &#xA;

    &#xA;

    &#xA;

    As I understand I should use integers and set them values 2 and 3. I want to get output like this

    &#xA;

    &#xA;
      &#xA;
    • MovieName.2.eng.srt

      • &#xA;

    • MovieName.3.eng.srt

      • &#xA;

    &#xA;

    &#xA;

    If it easier to extract all subs, let it be. I tried to do this too but I dont know how to set integers and use them :(&#xA;So what I should do ?&#xA;Thanks in advance

    &#xA;

  • What's the most elegant way to get the language codes from an MKV file with multiple audio tracks ?

    30 janvier 2017, par WackGet

    I need a way to get the language codes from MKV files which have multiple audio tracks.

    ffmpeg produces output which I could then filter using regular expressions but it doesn’t seem very elegant :

    $ ffmpeg -i file.mkv 2>&amp;1 | grep Audio
    
Stream #0:1(eng): Audio: mp2, 48000 Hz, stereo, s16, 192 kb/s (default)
    
Stream #0:2(nar): Audio: mp2, 48000 Hz, mono, s16, 64 kb/s (default)

    mediainfo has the ability to extract language information but in files with multiple tracks, it concatenates the codes into a single string :

    $ mediainfo file.mkv --inform="Audio;%Language%"  
    
ennar

    Is there a tool or command which will return language codes for multiple tracks in a nicer way, or a tool which would let me specify a track number and return the language code for that track only ?

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