[FFmpeg-trac] #290(FFmpeg:new): alpha channel not preserved when transcoding

FFmpeg trac at avcodec.org
Mon Jun 20 23:32:36 CEST 2011

#290: alpha channel not preserved when transcoding
  Reporter:  matteosistisette  |      Owner:  michael
      Type:  defect            |     Status:  new
  Priority:  critical          |  Component:  FFmpeg
   Version:  unspecified       |   Keywords:
Blocked By:                    |   Blocking:
Reproduced:  0                 |   Analyzed:  0
 When transcoding an flv file which has an alpha channel into a video or
 image file using codecs that support alpha channel (such as h264, or Apple
 Animation (qtrle), or PNG) the alpha channel is lost and the output video
 has an opaque background.

 An example flv input file with transparency can be downloaded from

 It has alpha channel. H264, Apple Animation and PNG all support alpha
 channel, so if any of these is used as the encoder and if the input video
 has alpha channel, the alpha channel should be preserved by default when

Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/290>
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