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• avcodec_decode_video2 takes long time to decode wmv

  22 février 2013, par Mike Versteeg

  I have written a player using the ffmpeg libraries that plays several avi, mp4 and mpg files fine but not wmv. Debugging has shown that the culprit is avcodec_decode_video2 which for some reason takes half a second to decode a single wmv frame. I have tested and confirmed this with multiple wmv files, even those with much lower resolution then other files that play successfully. Anyone has a clue what I'm doing wrong ?

  PS : log shows "Extra data : 8 bits left, value : 0" and "parser not found for codec wmav2, packets or times may be invalid." for WMV files.

  UPDATE :
  Further examination has shown the call to avcodec_decode_video2 is not slow, instead it seems to return the same frame some 16 times or so, giving the visual impression that it is slow. It does not return an error code so I have no clue why it won't decode all frames in the case of wmv.

  Relevant code :

    AVPacket packet;
  
    av_init_packet(&packet);
  
    done = pOwner->av_read_frame(pFormatCtx, &packet) < 0;
  
    if (!done && packet.stream_index==videostream) 
  
        bool error = pOwner->avcodec_decode_video2(pVCodecCtx, pFrameYUV, &finished, &packet) < 0;

• Capturing Clear Stills from H264 Stream

  22 octobre 2013, par David Findlay

  I'm trying to capture still images from a H264 wireless IP camera using FFMPEG. I found a similar question here : How can I extract a good quality JPEG image from an H264 video file with ffmpeg ?

  ffmpeg -y -i rtsp://10.2.69.201:554/ch0_0.h264 -r 10 -f image2 /var/www/camera.jpg

  I've implemented it as shown in that example. You can see a sample of the image I'm getting here : http://storm.woodypointcomms.com.au/camera.jpg. Basically the issue is the bottom part of the image is always blocky. If the sky has more detail and clouds the whole bottom half of the image may be blocky or blurry.

  My camera has limited stream options. One of which is I-Frame interval, you can vary it between 25-100 kbps.

  Does anyone have some suggestions about how I can get a better image ?

• Combining Video and Audio of different length in bulk

  27 avril 2017, par user2981223

  I am going through a tv series right now and editing the files to be to my liking. I have one set which has the video I want and one set that has the audio. I have a batch file that I can run that takes the video from every file in folder "A" and the audio from every file in folder "B" and outputs it to a folder named "output." But with this particular series, that is only half of what I need done.

  At the end of every episode of the files in the "B" folder there are some extra things. What I would like to do is take the audio and video from "A" and the audio from "B", combine it all into one file and also take the "A" and "B" files, compare the time stamps, and add the extra video from "B" to the output file.

  Let me put it another way. Let’s say "A" is 1080p with Japanese audio and is 20 minutes long. Let’s say "B" is 720p with English audio and is 23 minutes long. I want the whole 1080p video with both audio tracks, plus the 720p video spliced onto the end. Both files start at the same spot so syncing isn’t an issue. The issue is that the difference in time is different for every episode. So some episodes are 3 minutes longer, some only 30 seconds. Is there a way to make ffmpeg or another tool look at the difference in times and just add the excess to the output file ?

  Sorry for being long winded. Thanks for any help and guidance.