Recherche avancée

Sur d’autres sites (12449)

• Compression of a video with constant background

  28 juin 2017, par Spirou003

  (sorry if my english is bad, I can read it but I don’t write it quite well...)

  I want to compress some videos, which have two particularities :

  • there is a background that covers 90% of the area, during the whole video
  • most of the others elements can be separately described by a picture in move

  My videos are like this one, and don’t have audio. As you can see, almost everything can be described only by using a fixed background, few small images in move, plus a noise. Moreover, this noise will be almost nul and then an entropic coding would be very efficient. I think it will produce tiny files (< 5 Mo) even if the duration is in hours, a result that is very appreciable since I have actually recorded 30h of game (actual size is 3 Go).

  Is there any way to get new video files, that benefit of these informations ? If yes, what are the implication of a such encoding for watching these videos with Windows Media Player, or for usage with ffmpeg ?

  I searched with Google after anything that can help me, but I don’t know which keyword I can use for this, then I didn’t found anything usefull :-(

  Thanks in advance :-)

  PS : another example, the video is accelerated but shows the interesting moves

• FFmpeg generic error in an external library

  13 octobre 2017, par Mher Didaryan

  I’m trying to encode the game play from Unreal Engine with h264_nvenc encoder on a windows with FFmpeg 3.3.3. FFmpeg was configured with —enable-cuda —enable-cuvid —enable-nvenc
  However avcodec_open2 can’t open the codec.

  Below is the function where call to avcodec_alloc_context3 is.

  void Encoder::AddStream(AVCodecID CodecID)
  
  {
  
  
  
  VideoCodec = avcodec_find_encoder(CodecID);
  
  if (!VideoCodec) {
  
      UE_LOG(LogTemp, Error, TEXT("Could not find encoder for '%s'"), ANSI_TO_TCHAR(avcodec_get_name(CodecID)));
  
  }
  
  
  
  VideoSt.Stream = avformat_new_stream(FmtCtx, nullptr);
  
  if (!VideoSt.Stream) {
  
      UE_LOG(LogTemp, Error, TEXT("Could not allocate stream"));
  
  }
  
  
  
  VideoSt.Stream->id = FmtCtx->nb_streams - 1;
  
  VideoSt.Ctx = avcodec_alloc_context3(VideoCodec);
  
  if (!VideoSt.Ctx) {
  
      UE_LOG(LogTemp, Error, TEXT("Could not alloc an encoding context"));
  
  }
  
  
  
  VideoSt.Ctx->codec_id = CodecID;
  
  VideoSt.Ctx->flags = 0;
  
  VideoSt.Ctx->me_range = 16;
  
  VideoSt.Ctx->max_qdiff = 4;
  
  VideoSt.Ctx->refs = 0;
  
  VideoSt.Ctx->qmin = 2;
  
  VideoSt.Ctx->qmax = 31;
  
  VideoSt.Ctx->qcompress = 0.6;
  
  VideoSt.Ctx->width = ViewportSize.X;
  
  VideoSt.Ctx->height = ViewportSize.Y;
  
  VideoSt.Ctx->bit_rate = 4000000;
  
  VideoSt.Stream->time_base = VideoSt.Ctx->time_base = { 1, 30 };
  
  VideoSt.Ctx->gop_size = 25;
  
  VideoSt.Ctx->max_b_frames = 0;
  
  VideoSt.Ctx->thread_count = 1;
  
  VideoSt.Ctx->pix_fmt = AV_PIX_FMT_YUV420P;
  
  VideoSt.Ctx->codec_type = AVMEDIA_TYPE_VIDEO;
  
  
  
  if (FmtCtx->oformat->flags & AVFMT_GLOBALHEADER)
  
      VideoSt.Ctx->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;
  
  
  
  }

  As answer to this question suggests same issue I use avcodec_alloc_context3. Am I doing something wrong or error caused buy another reason ?

  Below is the part where call to avcodec_open2 is. It’s called after Encoder::AddStream so everything is set up I guess.

  auto c = VideoSt.Ctx;
  
  AVDictionary* opt = nullptr;
  
  av_dict_copy(&opt, Opt, 0);
  
  auto ret = avcodec_open2(c, VideoCodec, &opt);

  What can cause Generic error in an external library ?

• Is there a way to use youtube-dl in async

  8 octobre 2024, par Stam Kaly

  I have an application where I use zmq with asyncio to communicate with the clients who have the ability to download a video with youtube-dl to the server. I tried adding await to youtube_dl's download function but it gave me an error since it was not a coroutine. My code right now is simply looking like this :

  &#xA;&#xA;

  import asyncio
import youtube_dl


async def networking_stuff():
    download = True
    while True:
        if download:
            print("Received a request for download")
            await youtube_to_mp3("https://www.youtube.com/watch?v=u9WgtlgGAgs")
            download = False
        print("Working..")
        await asyncio.sleep(2)


async def youtube_to_mp3(url):
    ydl_opts = {
        'format': 'bestaudio/best',
        'postprocessors': [{
            'key': 'FFmpegExtractAudio',
            'preferredcodec': 'mp3',
            'preferredquality': '192',
        }]
    }

    with youtube_dl.YoutubeDL(ydl_opts) as ydl:
        ydl.download([url])


loop = asyncio.get_event_loop()
loop.create_task(networking_stuff())
loop.run_forever()


  &#xA;&#xA;

  which gives the following output :

  &#xA;&#xA;

  Received a request for download
[youtube] u9WgtlgGAgs: Downloading webpage
[youtube] u9WgtlgGAgs: Downloading video info webpage
[youtube] u9WgtlgGAgs: Extracting video information
[youtube] u9WgtlgGAgs: Downloading MPD manifest
[download] Destination: The Cardigans - My Favourite Game “Stone Version”-u9WgtlgGAgs.webm
[download] 100% of 4.20MiB in 00:03
[ffmpeg] Destination: The Cardigans - My Favourite Game “Stone Version”-u9WgtlgGAgs.mp3
Deleting original file The Cardigans - My Favourite Game “Stone Version”-u9WgtlgGAgs.webm (pass -k to keep)
Working..
Working..
....
Working..
Working..


  &#xA;&#xA;

  whereas I would expect the Working.. message to be printed in between youtube-dl's messages as well. Am I missing something here or is this impossible with async/await ? Is ffmpeg blocking ? If so, can I run the download in async without converting to mp3 or is using threads the only way ?

  &#xA;