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• FFmpeg library is detecting pixel format of VP9 video stream not correctly

  6 avril 2023, par Pikachu

  I am using a C code to detect pixel format of VP9 video stream in a WebM container. FFmpeg version 6.0, full shared library build, downloaded from official website. Operating system is Windows 10. I feed the library with a VP9 video encoded with alpha channel, pixel format is YUVA420p. It detects pixel format as YUV420p.

  


  I have found a similar question on StackOverflow.com, Is there a way to force FFMPEG to decode a video stream with alpha from ​a WebM video encoded with libvpx-vp9 ?, but it does not actually help.

  


  When I override the decoder with a libvpx, it continues to detect the pixel format as YUV420p instead of YUVA420p.

  


  C code is following. Note that error handling in code is omitted here for StackOverflow question to be shorter.

  


  AVFormatContext *fmt_ctx = NULL;
int err = avformat_open_input(&fmt_ctx, infp, NULL, NULL);
err = avformat_find_stream_info(fmt_ctx, NULL);
int stream = av_find_best_stream(fmt_ctx, AVMEDIA_TYPE_VIDEO, -1, -1, NULL, 0);
AVCodecParameters *codecpar = fmt_ctx->streams[stream]->codecpar;

const AVCodec *codec = NULL;
if (codecpar->codec_id == AV_CODEC_ID_VP9) {
    codec = avcodec_find_decoder_by_name(CODEC_LIBVPX_VP9);
} else {
    codec = avcodec_find_decoder(codecpar->codec_id);
}

AVCodecContext *ctx = avcodec_alloc_context3(codec);
err = avcodec_parameters_to_context(ctx, codecpar);
av_log(NULL, AV_LOG_DEBUG, "Pixel format: %d.\n", ctx->pix_fmt); //TODO:DEBUG.
err = avcodec_open2(ctx, codec, NULL);


  


  The program tells Pixel format: 0., which means AV_PIX_FMT_YUV420P, not the AV_PIX_FMT_YUVA420P !

  


  If I override pixel format manually, I am able to decode video with alpha channel and to see the transparent background, but it breaks the logics, because when a real YUV420p pixel format comes in and gets overridden by YUVA420p, this will be a problem.

  


  if (codecpar->codec_id == AV_CODEC_ID_VP9) {
    if (strcmp(codec->name, CODEC_LIBVPX_VP9) == 0) {
        if (ctx->pix_fmt == AV_PIX_FMT_YUV420P) {
            ctx->pix_fmt = AV_PIX_FMT_YUVA420P;
        }
    }
}


  


  At the same time ffmpeg tool started from command line with libvpx decoder tells that my video has YUVA420p pixel format. Output is following.

  


  D:\Temp\4>ffmpeg -c:v libvpx-vp9 -i yuva.webm
ffmpeg version 6.0-full_build-www.gyan.dev Copyright (c) 2000-2023 the FFmpeg developers
  built with gcc 12.2.0 (Rev10, Built by MSYS2 project)
  configuration: --enable-gpl --enable-version3 --enable-shared --disable-w32threads --disable-autodetect --enable-fontconfig --enable-iconv --enable-gnutls --enable-libxml2 --enable-gmp --enable-bzlib --enable-lzma --enable-libsnappy --enable-zlib --enable-librist --enable-libsrt --enable-libssh --enable-libzmq --enable-avisynth --enable-libbluray --enable-libcaca --enable-sdl2 --enable-libaribb24 --enable-libdav1d --enable-libdavs2 --enable-libuavs3d --enable-libzvbi --enable-librav1e --enable-libsvtav1 --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxavs2 --enable-libxvid --enable-libaom --enable-libjxl --enable-libopenjpeg --enable-libvpx --enable-mediafoundation --enable-libass --enable-frei0r --enable-libfreetype --enable-libfribidi --enable-liblensfun --enable-libvidstab --enable-libvmaf --enable-libzimg --enable-amf --enable-cuda-llvm --enable-cuvid --enable-ffnvcodec --enable-nvdec --enable-nvenc --enable-d3d11va --enable-dxva2 --enable-libvpl --enable-libshaderc --enable-vulkan --enable-libplacebo --enable-opencl --enable-libcdio --enable-libgme --enable-libmodplug --enable-libopenmpt --enable-libopencore-amrwb --enable-libmp3lame --enable-libshine --enable-libtheora --enable-libtwolame --enable-libvo-amrwbenc --enable-libilbc --enable-libgsm --enable-libopencore-amrnb --enable-libopus --enable-libspeex --enable-libvorbis --enable-ladspa --enable-libbs2b --enable-libflite --enable-libmysofa --enable-librubberband --enable-libsoxr --enable-chromaprint
  libavutil      58.  2.100 / 58.  2.100
  libavcodec     60.  3.100 / 60.  3.100
  libavformat    60.  3.100 / 60.  3.100
  libavdevice    60.  1.100 / 60.  1.100
  libavfilter     9.  3.100 /  9.  3.100
  libswscale      7.  1.100 /  7.  1.100
  libswresample   4. 10.100 /  4. 10.100
  libpostproc    57.  1.100 / 57.  1.100
[libvpx-vp9 @ 000001ecdf6002c0] v1.13.0-71-g45dc0d34d
    Last message repeated 1 times
Input #0, matroska,webm, from 'yuva.webm':
  Metadata:
    ENCODER         : Lavf60.3.100
  Duration: 00:00:05.55, start: 0.000000, bitrate: 227 kb/s
  Stream #0:0: Video: vp9 (Profile 0), yuva420p(tv, progressive), 1920x1080, SAR 1:1 DAR 16:9, 60 fps, 60 tbr, 1k tbn
    Metadata:
      alpha_mode      : 1
      ENCODER         : Lavc60.3.100 libvpx-vp9
      DURATION        : 00:00:05.550000000
At least one output file must be specified


  


  Here is my YUVA420p in the first video stream at the end of the console output :

  


  Stream #0:0: Video: vp9 (Profile 0), yuva420p(tv, progressive), 1920x1080, SAR 1:1 DAR 16:9, 60 fps, 60 tbr, 1k tbn


  


  


  The questions are following.

  


  

  1. How to detect real pixel format of VP9 video with FFmpeg library in C code reliably ?

  


  2. Why is the C code not detecting the actual pixel format even with codec overriden to libvpx ?

  


  


  Thank you.

  


• why ffmpeg process successfully terminated with return code of 1 without play anything

  24 juillet 2023, par Exc

  `I tried replacing youtube_dl with yt_dlp and replaced some of the code, the code worked fine but when using the command, the bot doesn't play music but immediately ffmpeg process 15076 successfully terminated with return code of 1

  


  Is there a problem with my code or the ffmpg option or ytdlp option that doesn't support the yt_dlp library ?`

  


   self.YTDL_OPTIONS = {
        'format': 'bestaudio/best',
        'outtmpl': 'F:/DISCORD BOT/Ex/music/%(extractor)s-%(id)s-%(title)s.%(ext)s',
        'restrictfilenames': True,
        'retry_max': 'auto',
        'noplaylist': True,
        'nocheckcertificate': True,
        'ignoreerrors': True,
        'logtostderr': False,
        'quiet': True,
        'no_warnings': True,
        'default_search': 'auto',
        'source_address': '0.0.0.0',
        'postprocessors': [{
            'key': 'FFmpegExtractAudio',
            'preferredcodec': 'mp3',
            'preferredquality': '192',
        }],
        'youtube_api_key': 'api'
    }
self.FFMPEG_OPTIONS = {
         'before_options': '-reconnect 1 -reconnect_streamed 1 -reconnect_delay_max 5',
         'options': '-vn',
         'executable':r'F:\DISCORD BOT\Ex\ffmpeg\bin\ffmpeg.exe'
         }

    
    @commands.hybrid_command(
        name="play",
        aliases=["p"],
        usage="",
        description="KARAUKENAN.",
         
    )
    @app_commands.describe(
        judul_lagu="link ato judul lagunya"
    )
    async def play(self, ctx, judul_lagu:str):
        await ctx.defer()
        voice_channel = ctx.author.voice
        if not voice_channel or not voice_channel.channel:
            await ctx.send("Join voice channel dulu gblk!")
            return

        voice_channel = voice_channel.channel
        song = self.search_song(judul_lagu)
        if not song:
            await ctx.send("Lagnya tdk ditemukan, coba keword lain.")
            return

        if not self.bot.voice_clients:
            voice_client = await voice_channel.connect()
        else:
            voice_client = self.bot.voice_clients[0]
            if voice_client.channel != voice_channel:
                await voice_client.move_to(voice_channel)

        self.music_queue.append([song, voice_client])
        if not self.is_playing:
            await self.play_music(ctx)
    
    async def play_music(self, ctx):
        self.is_playing = True
        while len(self.music_queue) > 0:
            song = self.music_queue[0][0]
            voice_client = self.music_queue[0][1]
            await ctx.send(f"Playing {song['title']}")

            voice_client.play(discord.FFmpegPCMAudio(song['source'], **self.FFMPEG_OPTIONS), after=lambda e: self.play_next())
            voice_client.is_playing()

            while voice_client.is_playing():
                await asyncio.sleep(1)

            self.music_queue.pop(0)
            self.is_playing = False

        await ctx.send("Queue is empty.")
        voice_client.stop()

    def play_next(self):
        if len(self.music_queue) > 0:
            self.is_playing = False

    def search_song(self, judul_lagu):
        ydl = yt_dlp.YoutubeDL(self.YTDL_OPTIONS)
        with ydl:
            try:
                info = ydl.extract_info(f"ytsearch:{judul_lagu}", download=False)['entries'][0]
                return {'source': info['formats'][0]['url'], 'title': info['title']}
            except Exception:
                return None




  


  when i use /play the bot sucess serch song but immediately terminate does not play any music

  


  2023-04-10 13:06:45 INFO     discord.voice_client Connecting to voice...
2023-04-10 13:06:45 INFO     discord.voice_client Starting voice handshake... (connection attempt 1)
2023-04-10 13:06:46 INFO     discord.voice_client Voice handshake complete. Endpoint found singapore11075.discord.media
2023-04-10 13:06:50 INFO     discord.player ffmpeg process 15076 successfully terminated with return code of 1.


  


  this image whe i use /play

  


• Using ffmpeg to merge video segments created by the MediaRecorder API

  10 avril 2023, par Dario Cimmino

  I am recording a live video from a webcam using mediarecorder API un chunks of 3 seconds :

  


  startButton.addEventListener('click', () => {
navigator.mediaDevices.getUserMedia({
    video: {
        width: 1280,
        height: 720,
        frameRate: { ideal: 30, max: 30 }
    }
})
    .then(stream => {
        video.srcObject = stream;
        mediaRecorder = new MediaRecorder(stream, { mimeType: 'video/webm' });
        mediaRecorder.ondataavailable = async (event) => {
            const blob = new Blob([event.data], { type: 'video/mp4' });
            const formData = new FormData();
            formData.append('segment', blob, `segment${segmentNumber}.mp4`);

            // When a new video segment is ready
            fetch('http://localhost:3000/upload', {
                method: 'POST',
                body: formData
            })
                .then((response) => response.text())
                .then((result) => {
                    console.log('Upload result:', result);
                })
                .catch((error) => {
                    console.error('Error uploading video segment:', error);
                });
            //Upload data to mysql
            fetch('upload.php', {
                method: 'POST',
                body: formData
            })
                .then(response => response.text())
                .then(result => {
                    console.log('Upload result to MYSQL:', result);
                })
                .catch(error => {
                    console.error('Error uploading video segment to MYSQL:', error);
                });
            segmentNumber++;
        };

        mediaRecorder.start(3000);
    })
    .catch(error => {
        console.error('Error accessing camera:', error);
    });


  


  }) ;

  


  I am left with only the first segment playable, as is expected.

  


  How ever when the recording stops, i'd like to merge all those segments recorded using ffmpeg (or any other) with the help of my nodeJs server.

  


  I am having difficulty understand the parsing of mp4 files.

  


  if I try the command :

  


  ffmpeg -i segment1.mp4 -i segment2.mp4 -i segment3.mp4  out.mp4


  


  I get the following error :

  


      ffmpeg version N-110223-gb18a9c2971-20230410 Copyright (c) 2000-2023 the FFmpeg developers
  built with gcc 12.2.0 (crosstool-NG 1.25.0.152_89671bf)
  configuration: --prefix=/ffbuild/prefix --pkg-config-flags=--static --pkg-config=pkg-config --cross-prefix=x86_64-w64-mingw32- --arch=x86_64 --target-os=mingw32 --enable-gpl --enable-version3 --disable-debug --disable-w32threads --enable-pthreads --enable-iconv --enable-libxml2 --enable-zlib --enable-libfreetype --enable-libfribidi --enable-gmp --enable-lzma --enable-fontconfig --enable-libvorbis --enable-opencl --disable-libpulse --enable-libvmaf --disable-libxcb --disable-xlib --enable-amf --enable-libaom --enable-libaribb24 --enable-avisynth --enable-chromaprint --enable-libdav1d --enable-libdavs2 --disable-libfdk-aac --enable-ffnvcodec --enable-cuda-llvm --enable-frei0r --enable-libgme --enable-libkvazaar --enable-libass --enable-libbluray --enable-libjxl --enable-libmp3lame --enable-libopus --enable-librist --enable-libssh --enable-libtheora --enable-libvpx --enable-libwebp --enable-lv2 --disable-libmfx --enable-libvpl --enable-openal --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenh264 --enable-libopenjpeg --enable-libopenmpt --enable-librav1e --enable-librubberband --enable-schannel --enable-sdl2 --enable-libsoxr --enable-libsrt --enable-libsvtav1 --enable-libtwolame --enable-libuavs3d --disable-libdrm --disable-vaapi --enable-libvidstab --enable-vulkan --enable-libshaderc --enable-libplacebo --enable-libx264 --enable-libx265 --enable-libxavs2 --enable-libxvid --enable-libzimg --enable-libzvbi --extra-cflags=-DLIBTWOLAME_STATIC --extra-cxxflags= --extra-ldflags=-pthread --extra-ldexeflags= --extra-libs=-lgomp --extra-version=20230410
  libavutil      58.  6.100 / 58.  6.100
  libavcodec     60.  9.100 / 60.  9.100
  libavformat    60.  4.101 / 60.  4.101
  libavdevice    60.  2.100 / 60.  2.100
  libavfilter     9.  5.100 /  9.  5.100
  libswscale      7.  2.100 /  7.  2.100
  libswresample   4. 11.100 /  4. 11.100
  libpostproc    57.  2.100 / 57.  2.100
Input #0, matroska,webm, from 'segment1.mp4':
  Metadata:
    encoder         : Chrome
  Duration: N/A, start: 0.000000, bitrate: N/A
  Stream #0:0(eng): Video: h264 (Constrained Baseline), yuv420p(progressive), 1280x720 [SAR 1:1 DAR 16:9], 30.30 fps, 30 tbr, 1k tbn (default)
[mov,mp4,m4a,3gp,3g2,mj2 @ 000001d93cf25fc0] Format mov,mp4,m4a,3gp,3g2,mj2 detected only with low score of 1, misdetection possible!
[mov,mp4,m4a,3gp,3g2,mj2 @ 000001d93cf25fc0] moov atom not found
segment2.mp4: Invalid data found when processing input


  


  any help or inputs are appreciated. THanks !