Re: [FFmpeg-devel] [PATCH 0/7] Container level frame cropping parameters

[James Almer <jamrial@gmail.com>]

On 10/10/2023 8:17 AM, Anton Khirnov wrote:
> Quoting James Almer (2023-10-07 18:24:56)
>> This is a simple set to add support to stream wide, container level cropping
>> parameters, as featured in formats like Matroska and ISOBMFF. It's needed for
>> things like AV1 streams generated by certain hardware encoders that produce
>> dimension aligned output, and unlike H26x, can't export cropping info within
>> the bitstream.
>> In this set i add the packet side data type, mux and demux support to Matroska,
>> and handling code to ffmpeg and ffplay. Missing is support for clap boxes in
>> ISOBMFF, and exporting the relevant side data from encoders like AMF.
>>
>> It's a rebased and updated version to the set i sent a month ago.
> 
> Why is there no lavc-decoder handling? I would expect cropping side data
> submitted to lavc to be somehow propagated to decoded frames.
> Though there is a question of how to combine side data with the
> codec-level cropping.

I thought about adding lavc support alongside the CLI handling, yeah. 
And it should be a matter of adding the values to the existing ones in 
frame->crop_* as exported by decoders, which av_frame_apply_cropping() 
will then handle.

And the reason i add support to the CLI by including a filter instead of 
leaving it up to lavc is that av_frame_apply_cropping() may not do exact 
cropping if AV_CODEC_FLAG_UNALIGNED is not set.
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