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

[Anton Khirnov]

Quoting James Almer (2023-10-10 13:44:19)
> 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.

I intend to have the CLI always set AVCodecContext.apply_cropping=0 and
have it handled by lavfi for this exact reason, just didn't get to
actually doing it yet. Feel free and welcome to do it yourself.

-- 
Anton Khirnov