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• Incorrect height for U and V channel when creating video from jpgs using ffmpeg

  27 juillet 2022, par Chu Bun

  I use the method in the ffmpeg source sample decode_video.c to decode a series of jpgs into AVFrames. Then use the method in the sample encode_video.c to combine the AVFrames into a video file.

  


  AV_CODEC_ID_MJPEG is used to set up the decoder for the jpgs. The output frames have the format AV_PIX_FMT_YUVJ422P which has (full-width x full-height) Y-channel, and (half-width x full-height) U and V channels. The problem is when I try to encode the frames, ffmpeg seems to expect (half-width x half-height) U and V channels. As a result the colors are stretch in the vertical direction and do not match with the image in the Y-channel.

  


  I could not figure out how to either decode the jpgs into YUV420 (half-width x half-height) frames, or encode frames in YUV422 format. Any pointers ?

  


• DirectShow stream using ffmpeg point to point streaming through TCP protocol

  12 juillet 2017, par Jānis Biedriņš

  I had set up a point-to-point stream using ffmpeg via UDP protocol and the stream worked, but there was screen tearing etc. I already tried raising the buffer size, but it did not help. This is a work network, so the UDP protocol won’t work.
  here is the full command :

  ffmpeg -f dshow  -i video="UScreenCapture"  -r 30 -vcodec mpeg4 -q 12 -f mpegts udp://192.168.1.220:1234?pkt_size=188?buffer_size=65535

  I’ve tried to make this work with TCP with no success
  Here’s what i’ve got now :

  ffmpeg -f dshow -i video="UScreenCapture" -f mpegts tcp://192.168.1.194:5555

  this returns an error :

  real-time buffer [UScreenCapture] [Video input] too full or near too
  full <323% of size : 3041280 [rtbufsize parameter]> ! frame dropped !

  This last message repeated xxxx times (it went up to around 1400 and I just turned it off).

  I’ve tried to implement the -rtbufsize paremeter and raising the buffsize up to 800000000, didn’t help.

  I would appreciate any suggestions on how to solve this.

• FFMPEG command to mix audio and video with adjustable volume, plays till Video length and loop audio entire video

  10 mai 2020, par Tomin

  I have :

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  • Video file of X length

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  • Audio of Y length

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  I am trying to achieve an output video that has the following qualities :

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  1. The volume level of the added audio should be adjustable

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  2. The audio should loop till the end of the video

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  3. It should not break even if the input video does not have any audio

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  4. I should be able to mute the audio of the source video if needed.

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  5. All of the above, in the fastest possible way.

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  I'm not well versed with FFMPEG, maybe some experts could help.

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