[Libav-user] Analyzing frames WITHOUT deinterlacing.
Carl Eugen Hoyos
cehoyos at ag.or.at
Wed Jun 29 09:13:12 CEST 2016
David Harrison <dosirrah at ...> writes:
> I have been handed a tool that analyzes frames along with
> its source code.
Where can I find this tool?
> The tool uses libav.
Note that only FFmpeg is supported here.
> In some cases the video input to this tool is interlaced.
> The tool operates just fine, but because my intent is not
> to render the video but to extract and analyze features
> from the video I would prefer to analyze the video in a
> lossless manner.
libavcodec is bit-exact by default for codecs that define
an exact (lossless) output (mpegvideo does not iirc).
> In other words, I DO NOT want to deinterlace the video.
This is the default, deinterlacing was removed from
libavcodec, you need to specify a deinterlacing filter
> I would rather operate on half fields.
What kind of input do you provide? For all "real" codecs,
there is only frame output, there are encoders that
produce field-encoded files for j2k and hevc but FFmpeg so
far does not support merging the fields automatically (as
required for every usecase I can think of).
If FFmpeg would not provide frame output for mpeg2video,
h264 and vc1, it would not be lossless and not bit-exact.
(vc1 usually is not bit-exact but this is unrelated.)
The specifications all require frame output and this is
what the reference (and hardware) decoders do.
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