[x264-devel] Corrupted slices

[BugMaster]

On Sun, 22 Oct 2023 22:37:06 +0300, BugMaster wrote:
> On Mon, 16 Oct 2023 18:25:41 +0200, Jan Brothánek wrote:
>> Hi,

>> After testing I confirm the output doesn't contain corrupted slices. But
>> VBV overflow is present quite often. Is that considered a bug, or is it
>> just a risk of the slice mode which needs to be accepted? My TS muxer is
>> strict for VBV requirements in low latency mode. I use slices to achieve
>> the lowest latency but if VBV compliance isn't guaranteed in slice mode,
>> that won't be an option.

>> If you'd like to reproduce the VBV overflows, I've concatenated some pieces
>> of my testing video here:
>> https://drive.google.com/file/d/1Fgak--50bRcQrJUDDe8Jw8BkbvLY-Yzo/view?usp=sharing

>> and I reproduce using this command (--tff for even more VBV overflows, but
>> it's present using progressive too):

>> x264 --tff --bitrate 8000 --vbv-bufsize 1600 --vbv-maxrate 8000
>> --output-depth 10 --profile high422 --output-csp i422 --preset ultrafast
>> --tune zerolatency --slices 16 --threads 16 -I 120 -b 0 -o output.mp4
>> input.cat.mp4

>> I see 5 warnings about "VBV underflow" and even more cases if I compute the
>> buffer fullness manually based on the codestream sizes (return values of
>> x264_encoder_encode()) which I dumped. One of the frames was even 233767B
>> which itself won't fit to the VBV buffer.

>> Best,
>> Jan

> Hi.

> Try with this patch:
> https://code.videolan.org/BugMaster/x264/-/commit/8409bcbf3a326ee0950011f0560ce69e900a017d

> This is probably the maximum that I can do without radically changing
> the predictors, which sometimes go crazy when there is a practically
> unchanged frame in the stream for a long time, and then there is a
> sudden movement.

> At least I hope that with this patch you won't have VBV underflows.
> And in the 2-pass mode there will also be no corrupted slices.


Updated version. Fixed some rare "damaged fragments" in input.cat.mp4
https://code.videolan.org/BugMaster/x264/-/commit/d46938dec10ceab74eb26d281d434fa284c7fbb9