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• ffmpeg audio out of sync with video stacking

  3 avril 2024, par s0mbre

  The problem

  


  When trying to do horizontal stacking of two videos in ffmpeg, the combined audio track loses sync with the video on the second input. As far as I've look it up, this problem is very common, not to say notorious with ffmpeg.

  


  I do hstack muxing like this :

  


  ffmpeg -i 1.mp4 -i 2.mp4 -filter_complex \
"[0:v]scale=1280:-2,crop=w=640:h=720:x=0[v1]; \
[1:v]scale=1280:-2,crop=w=640:h=720:x=0[v2]; \
[v1][v2]hstack=shortest=1[v]; \
[0:a][1:a]amix=duration=shortest[a]" \
-map [v] -map [a] -c:v libx264 -c:a libmp3lame -r 30 -y stuff/out.mp4


  


  It encodes just fine as far as the hsplit goes. But the resulting video is out of sync with the audio : the second input (located on the right side in the resulting split) demonstrates about 3 sec. audio off-syncking, where the audio track is ahead of the picture. I realize this is somehow connected with the source videos' timestamps, but no popular remediation recipes helped (see below).

  


  What I expect

  


  I'd expect a resulting stacked video where the audio track is muxed with exact correspondence to the original input pictures.

  


  What I tried (all in vain !)

  


  Something I've tried but to no avail :

  


  

  1. Appending -async 1 option as suggested here and here

  


  2. Using the aresample=async=1 or aresample=async=1000 filter on each audio input as suggested here and here

  


  3. Padding each audio track with apad as suggested here

  


  4. Using the adelay=0 and adelay=[delay]s filters on the failing input

  


  5. Changing the audio codec to a number of alternatives (aac etc.)

  


  6. Infinite combinations of 1-5 above...

  


  


  What seems indeed to work is manual passing a delay value to the -itsoffset filter as suggested here and in the docs and using the offset track as an extra (pure audio) input. But how do I find the exact offset with a different set of videos ?

  


  In short, I am at a standstill after 7+ days of ravenous search-and-try.

  


• ffmpeg command produces black image as output

  3 mars 2020, par Nishad DESHMUKH

  Input #0, video4linux2,v4l2, from ’/dev/video0’ :

  Duration : N/A, start : 13555.753906, bitrate : 147456 kb/s

  Stream #0:0: Video: rawvideo (YUY2 / 0x32595559), yuyv422, 640x480, 147456 kb/s, 30 fps, 30 tbr, 1000k tbn, 1000k tbc

  Stream mapping :

  Stream #0:0 -> #0:0 (rawvideo (native) -> mjpeg (native))

  Press [q] to stop, [?] for help
  [swscaler @ 0x55fd0eafa3e0] deprecated pixel format used, make sure you did set range correctly
  Output #0, image2, to ’test1.jpeg’ :

  Metadata :

  encoder         : Lavf57.83.100
  
  
  
  Stream #0:0: Video: mjpeg, yuvj422p(pc), 640x480, q=2-31, 200 kb/s, 30 fps, 30 tbn, 30 tbc
  
  
  
  Metadata:
  
  
  
    encoder         : Lavc57.107.100 mjpeg
  
  
  
  Side data:
  
  
  
    cpb: bitrate max/min/avg: 0/0/200000 buffer size: 0 vbv_delay: -1

  frame= 1 fps=0.0 q=1.6 Lsize=N/A time=00:00:00.03 bitrate=N/A speed=8.41x

  video:3kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead : unknown

• ffmpeg add semi transparent watermark(png) with different size

  20 septembre 2016, par Archer

  I’m trying to add a png watermark (with alpha channel) over h264 video with semi transparent. By using overlay filter I managed to add watermark to the video.

  ffmpeg -y -i input.mp4 -i watermark.png -filter_complex "[0][1] overlay=0:0" -c:v libx264 -an output.mp4

  But overlay filter does not provide transparent option. So I tried to use blend filter. However, when I use origin resolution, error message comes out.

  ffmpeg -y -i input.mp4 -i watermark.png -filter_complex "[0][1]blend=all_mode=overlay:all_opacity=0.3" -c:v libx264 -an output.mp4

  Output :

    libavutil      55. 28.100 / 55. 28.100
  
    libavcodec     57. 48.101 / 57. 48.101
  
    libavformat    57. 41.100 / 57. 41.100
  
    libavdevice    57.  0.101 / 57.  0.101
  
    libavfilter     6. 47.100 /  6. 47.100
  
    libavresample   3.  0.  0 /  3.  0.  0
  
    libswscale      4.  1.100 /  4.  1.100
  
    libswresample   2.  1.100 /  2.  1.100
  
    libpostproc    54.  0.100 / 54.  0.100
  
  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'input.mp4':
  
    Metadata:
  
      major_brand     : isom
  
      minor_version   : 512
  
      compatible_brands: isomiso2avc1mp41
  
      encoder         : Lavf57.41.100
  
    Duration: 00:00:45.08, start: 0.000000, bitrate: 1872 kb/s
  
      Stream #0:0(und): Video: h264 (Baseline) (avc1 / 0x31637661), yuv420p, 1920x1080, 1869 kb/s, 29.72 fps, 30 tbr, 16k tbn, 32k tbc (default)
  
      Metadata:
  
        handler_name    : VideoHandler
  
  Input #1, png_pipe, from 'watermark.png':
  
    Duration: N/A, bitrate: N/A
  
      Stream #1:0: Video: png, rgba(pc), 64x64, 25 tbr, 25 tbn, 25 tbc
  
  [Parsed_blend_0 @ 00750600] First input link top parameters (size 1920x1080, SAR 0:1) do not match the corresponding second input link bottom parameters (64x64, SAR 0:1)
  
  [Parsed_blend_0 @ 00750600] Failed to configure output pad on Parsed_blend_0
  
  Error configuring complex filters.
  
  Invalid argument

  The result looks like some resolution issue with the parameters. So that I tried to scale the watermark before blending.

  ffmpeg -y -i input.mp4 -i watermark.png -filter_complex "[0:0]scale=1920x1080[a]; [1:0]scale=1920x1080[b]; [a][b]blend=all_mode=overlay:all_opacity=0.3" -c:v libx264 -an output.mp4

  FFMPEG works with these parameters. But the output wasn’t I expected, because watermark had been stretched.
  Any idea to blend watermark with different resolution without stretching to video with transparency ?

  Here are the testing file. (ffmpeg version 3.1.2)
  https://drive.google.com/open?id=0B2X3VLS01TogdHVJZ2I1ZC1GUUU
  https://drive.google.com/open?id=0B2X3VLS01TogbjhuZTlBOFFpN1k