[FFmpeg-trac] #388(undetermined:closed): Bug with deinterlacing!

FFmpeg trac at avcodec.org
Mon Aug 15 19:04:15 CEST 2011

#388: Bug with deinterlacing!
Reporter:  Silent Rain  |       Owner:  michael
    Type:  defect       |      Status:  closed
Priority:  normal       |   Component:  undetermined
 Version:  unspecified  |  Resolution:  worksforme
Keywords:               |  Blocked By:
Blocking:               |  Reproduced:  0
Analyzed:  0            |
Changes (by cehoyos):

 * status:  open => closed
 * resolution:   => worksforme


 (ffmpeg command line and console output is still missing making this an
 invalid ticket.)

 While the content of your sample may be interlaced (I agree it is), the
 stream is encoded as progressive frames, afaict, so how should FFmpeg be
 able to know the stream is interlaced?

 Note that the 25fps progressive material that TV stations broadcast here
 via DVB is encoded as interlaced frames "50i" (50 fields per second, so
 every sane decoder delivers 25 progressive frames per second), so FFmpeg -
 semantically incorrectly - sets interlaced_frame. Generally, afaict, you
 have to visually inspect the material to decide if it is interlaced or

 Or in other words: You can take interlaced source material and encode it
 as progressive frames (try ffmpeg -i interlaced_file -qscale 2 to get a
 sample with maximum quality and still interlaced frames that yadif and
 vdpau deinterlace fine), so all flags in the stream show "progressive" as
 in your sample, or you can take progressive, 25fps material (or claim that
 24fps material is actually 25fps) and "pull it up" to 50 fields per
 seconds, then encode it interlaced (with the respective fields set) as it
 is done in case of DVB broadcast of films here, but if you use a de-
 interlacer after decoding, you (may) worsen the picture quality; without a
 de-interlacer, you get exactly the original 25 fps progressive material
 (wrongly assuming a lossless encoder).

 If you wanted to open a feature request for a video filter that reports if
 material is interlaced or not, please reword the ticket.

Ticket URL: <https://avcodec.org/trac/ffmpeg/ticket/388#comment:3>
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