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I have a QuickTime file .mov with alpha channel compressed with PNG codec. What I need is to create smaller version of this file using ffmpeg. Everything works except new mov has no alpha (Adobe After Effects and Premiere can see only RGB, ffprobe says new file has RBG and A channel. :| Please help.

This is the simplest version of my command line:

ffmpeg -i inPNG.mov -vcodec copy -y outPNG.mov

I tried the following switches without success:

  • -vcodec png
  • -pix_fmt rgb32 or bgra

Adobe Premiere says something interesting about newly created file: QuickTime Details: This is a referencing movie. No further detail is available.

Here is FFMPEG answer:

[ec2-user@domU-12-31-39-14-69-CF ec]$ ffmpeg -i "content/13400/13400 HD 1080.mov" -vcodec copy -y "content/13400/13400 HD 720.mov"
FFmpeg version SVN-r26400, Copyright (c) 2000-2011 the FFmpeg developers
  built on May 21 2012 22:25:19 with gcc 4.4.5 20110214 (Red Hat 4.4.5-6)
  configuration: --enable-avfilter --enable-libmp3lame --disable-mmx --arch=x86_64 --enable-libfaac --enable-nonfree --enable-filter=movie --enable-libx264 --enable-gpl
  libavutil     50.36. 0 / 50.36. 0
  libavcore      0.16. 1 /  0.16. 1
  libavcodec    52.108. 0 / 52.108. 0
  libavformat   52.93. 0 / 52.93. 0
  libavdevice   52. 2. 3 / 52. 2. 3
  libavfilter    1.74. 0 /  1.74. 0
  libswscale     0.12. 0 /  0.12. 0
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'content/13400/13400 HD 1080.mov':
  Metadata:
    major_brand     : qt
    minor_version   : 537199360
    compatible_brands: qt
    creation_time   : 2012-11-01 11:51:39
  Duration: 00:00:02.00, start: 0.000000, bitrate: 51822 kb/s
    Stream #0.0(eng): Video: png, bgra, 1920x1080, 51793 kb/s, PAR 1920:1920 DAR 16:9, 25 fps, 25 tbr, 25 tbn, 25 tbc
    Metadata:
      creation_time   : 2012-11-01 11:51:39
    Stream #0.1(eng): Data: tmcd / 0x64636D74, 0 kb/s
    Metadata:
      creation_time   : 2012-11-01 11:51:58
Output #0, mov, to 'content/13400/13400 HD 720.mov':
  Metadata:
    major_brand     : qt
    minor_version   : 537199360
    compatible_brands: qt
    creation_time   : 2012-11-01 11:51:39
    encoder         : Lavf52.93.0
    Stream #0.0(eng): Video: png, bgra, 1920x1080 [PAR 1:1 DAR 16:9], q=2-31, 51793 kb/s, 25 tbn, 25 tbc
    Metadata:
      creation_time   : 2012-11-01 11:51:39
Stream mapping:
  Stream #0.0 -> #0.0
Press [q] to stop encoding
frame=   50 fps=  0 q=-1.0 Lsize=   12646kB time=2.00 bitrate=51797.6kbits/s
video:12645kB audio:0kB global headers:0kB muxing overhead 0.008295%
share|improve this question
1  
How do you want to create a "smaller" version of the file if it's already compressed as PNG and all you're doing is copying the bitstream? This won't make the file smaller. But losing the alpha channel shouldn't happen, of course. Your FFmpeg version is almost two years old. Could you try a newer version and see if the problem persists? For Linux, try a static build linked to on the downloads page. –  slhck Nov 2 '12 at 21:22
    
Yes, I just simplified my command for adding question here. I know this doesn't make smaller file. But my problem is with losing Alpha channel. –  Artur Nov 2 '12 at 22:09

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