[Cin] AV1 yuv422p10le rendering with some output FFStream::seek I/O errors, seek fails

[Phyllis Smith]

*Summary* is that the error message is due to lack of keyframes and the
workaround is to use Transcode.
BUT hopefully a better solution with the Render format parameters can be
found.  The render fix for h264/h265 formats is the addition of the lines
below (which obviously is not pertinent to av1).  I will see if I can find
an alternative, but might not.

> # use framerate for 1 keyframe/sec, needed for seeks
> keyint_min=25                  (or keyint_min=30 for x265)
> x264-params=keyint=25   (or x265-params-keyint=30 for x265)
>

About the error message:

> FFStream::seek:
> /run/media/terje/Videoklipp/Cineform/av1_yuv422p10le_LP.webm
>  retry limit, pos=207 tstmp=8280,   err: Input/output error
> ** seek fail 207, 8280
>

Seeking Issues (
https://cinelerra-gg.org/download/CinelerraGG_Manual/Seeking_Issues.html)

> If you have an issue playing a video and not seeing it in the Compositor
> (just see a black
> screen), it is most likely due to the media not being designed to be
> editable. It is most likely
> not damaged. Generally it just does not have keyframes which are needed
> for seeking
> which is what is done when you move around the media and start playing in
> the middle.
> The media plays just fine in the compositor if you always play from the
> beginning because
> then you don’t need keyframes to seek. You can get around this problem if
> you proxy the
> media. A good choice to use for the proxy would be use scalar, ffmpeg/mp4
> and size of 1/2.
>
The proxied media can then seek and you will see it play in the compositor
> because keyframes exist.
>
Or use TRANSCODE which adds keyframes when media is not seekable (see
Manual for details). This is particularly useful for the mkv container,
which often has seek problems.

Just a reminder about the message below.

> FFMPEG::open_decoder: some stream times estimated:
>
This is not a problem. Basically, when you open a file if a stream has a
known duration, there is no message. If the duration is unknown, it is
estimated by using the File Size and Bitrate to estimate the duration.
----------------------------------------

My AV1 (video only) test run procedure using CinGG loading a 10-bit input
> file, resulted in 12% smaller file size than with h265. Visually the AV1
> output file seemingly is ok, but there are some CinGG output
> "FFStream::seek I/O errors, seek fails" I don't know what are  !?
>
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