[FFmpeg-devel] [PATCH 31/39] avcodec/encode: Always use intermediate buffer in ff_alloc_packet2()

[Michael Niedermayer]

On Fri, May 21, 2021 at 11:17:34AM +0200, Andreas Rheinhardt wrote:
> Up until now, ff_alloc_packet2() has a min_size parameter:
> It is supposed to be a lower bound on the final size of the packet
> to allocate. If it is not too far from the upper bound (namely,
> if it is at least half the upper bound), then ff_alloc_packet2()
> already allocates the final, already refcounted packet; if it is
> not, then the packet is not refcounted and its data only points to
> a buffer owned by the AVCodecContext (in this case, the packet will
> be made refcounted in encode_simple_internal() in libavcodec/encode.c).
> The goal of this was to avoid data copies and intermediate buffers
> if one has a precise lower bound.
> 
> Yet those encoders for which precise lower bounds exist have recently
> been switched to ff_get_encode_buffer() (which automatically allocates
> final buffers), leaving only two encoders to actually set the min_size
> to something else than zero (namely aliaspixenc and hapenc). Both of
> these encoders use a very low lower bound that is not helpful in any
> nontrivial case.
> 
> This commit therefore removes the min_size parameter as well as the
> codepath in ff_alloc_packet2() for the allocation of final buffers.
> Furthermore, the function has been renamed to ff_alloc_packet() and
> moved to encode.h alongside ff_get_encode_buffer().

breaks:

./ffmpeg -f lavfi -i testsrc=size=5632x3168 -pix_fmt yuv420p -vframes 1 -bitexact  -vcodec ffv1   -y ffv-bigrgb-tocket6005.avi

[ffv1 @ 0x559df8384f40] Cannot allocate worst case packet size, the encoding could fail
[ffv1 @ 0x559df8384f40] Failed to allocate packet of size 2147483551
Video encoding failed
Conversion failed!

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

If you fake or manipulate statistics in a paper in physics you will never
get a job again.
If you fake or manipulate statistics in a paper in medicin you will get
a job for life at the pharma industry.
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