[FFmpeg-devel] [PATCH] avcodec/h264_metadata: add change pic_order_cnt_type option

[sharpbai at gmail.com]

To Andreas Rheinhardt,

> It is unsafe in the sense that it can lead to invalid and broken files.
> But it is way safer than actually modifying the slice headers, because
> the latter is absolutely irreversible, whereas one just needs to set big
> enough values to fix files broken by setting too low values for
> reorder_frames and max_dec_frame_buffering. For this a warning in the
> documentation that wrong values might break files should suffice.

Got it.

> Just for confirmation: Setting num_reorder_frames to zero is not enough?

On my tested devices setting num_reorder_frames to zero is enough.
But I can't ensure it will be effective on every decoder.

 
> This is wrong: pic_order_cnt_lsb is typically incremented by two per
> frame (but it can be different), whereas frame_num is only incremented
> after a reference picture and only by 1. Furthermore, both these values
> are only coded modulo a certain power of two and these powers can be
> different.

I have found that only on macOS 11 pic_order_cnt_lsb is incremented by two
while on iOS 14 or other Android devices I have tested pic_order_cnt_lsb
is incremented by one. You could try to generate a bytestream on iOS to
verify it.


sharpbai
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