[FFmpeg-devel] [PATCH] Fix incorrect bitmap header in rawvideo AVI output and allow input of resulting files.

Michael Niedermayer michaelni
Sat Jul 28 14:00:03 CEST 2007


On Thu, Jul 26, 2007 at 06:07:48PM -0400, Martin Gentry wrote:
> Since I didn't get any response on the issue I was having with raw video
> output to AVI, attached is what I did to fix it.
> As stated in my earlier email on the topic, currently if the video is run
> through the raw video encoder the frame data seems to always be top-down
> thus always requiring a negative height in the AVI bitmap header, but the
> current code in SVN outputs a positive value resulting in an AVI that plays
> upside down in Windows Media Player.  Introducing the negative height to fix
> this rendered the output as unacceptable input for ffmpeg, so I made an
> attempt to fix that also, but don't know that my use of a flag that the raw
> video decoder looks at is the correct way to fix that.  Alternatively fixing
> this without introducing the negative height in the bitmap header would have
> necessitated always flipping the final data going through the raw encoder,
> which seemed a larger code modification and thus undesirable?
> So that said, I somewhat expect this to be rejected but am hoping that
> process will at least inform me as to a more correct way to fix the problem.

the avi raw flip problem is not an easy one to solve

also there are 2 problems
1. is reading raw avi properly with either vertical direction
2. is storing it properly

to solve 1. i would move the flip code from rawdec.c to avidec.c this
avoids a headache for the stream copy case between avi and non avi
also the flip code is avi specific not raw specific

to solve 2. i would simply always assume top down raw in avienc.c

also read:
(negtive height is invalid for anything but raw rgb)

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Opposition brings concord. Out of discord comes the fairest harmony.
-- Heraclitus
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