bgr0 -> bgra does not make the output opaque

[Carl Eugen Hoyos]

If I decode attached sample with current FFmpeg, pix_fmt is currently identified as bgr0, but on conversion to bgra, the output is transparent (instead of opaque).

ffmpeg -i out.avi -pix_fmt bgra out.png
ffmpeg version N-36363-g0af34c4, Copyright (c) 2000-2012 the FFmpeg developers
  built on Jan  3 2012 01:15:46 with gcc 4.5.3
  configuration: --cc='/usr/local/gcc-4.5.3/bin/gcc -m32'
  libavutil      51. 33.100 / 51. 33.100
  libavcodec     53. 50.100 / 53. 50.100
  libavformat    53. 29.100 / 53. 29.100
  libavdevice    53.  4.100 / 53.  4.100
  libavfilter     2. 57.101 /  2. 57.101
  libswscale      2.  1.100 /  2.  1.100
  libswresample   0.  5.100 /  0.  5.100
Input #0, avi, from 'out.avi':
  Metadata:
    encoder         : Lavf52.108.0
  Duration: 00:00:00.04, start: 0.000000, bitrate: 21647 kb/s
    Stream #0:0: Video: ffv1 (FFV1 / 0x31564646), bgr0, 256x256, 25 tbr, 25 tbn, 25 tbc
[buffer @ 0x8dcdd20] w:256 h:256 pixfmt:bgr0 tb:1/1000000 sar:0/1 sws_param:
[buffersink @ 0x8dced80] auto-inserting filter 'auto-inserted scale 0' between the filter 'src' and the filter 'out'
[scale @ 0x8dcf2e0] w:256 h:256 fmt:bgr0 -> w:256 h:256 fmt:bgra flags:0x4
Output #0, image2, to 'out.png':
  Metadata:
    encoder         : Lavf53.29.100
    Stream #0:0: Video: png, bgra, 256x256, q=2-31, 200 kb/s, 90k tbn, 25 tbc
Stream mapping:
  Stream #0:0 -> #0:0 (ffv1 -> png)
Press [q] to stop, [?] for help
frame=    1 fps=  0 q=0.0 Lsize=       0kB time=00:00:00.04 bitrate=   0.0kbits/s
video:191kB audio:0kB global headers:0kB muxing overhead -100.000000%

out.png is transparent

[Carl Eugen Hoyos]

Additional sample is attached to ticket #895.

[Michael Niedermayer]

Locally fixed