Store temporary frames as JPEG to save space about video2x HOT 5 CLOSED

The difference in quality is too big between PNG and JPEG. Therefore, this feature request will not be implemented at this point.

PNG

JPEG

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To be fair, and this is just additional technical info on the topic, it does look like the default jpg output in ffmpeg without specifying a quality rate is pretty poor not only from your test images but a brief test of my own. Selecting the jpg output quality is done using the same -q or -qscale modifiers like other codecs. Looks like it ranges from 2-32 for jpeg with 2 being the best and 32 being the worst. Not setting it, looks like with my test samples it was defaulting to about 24-25. Setting to 1 (before I found that it MAY be limited to a max of 2 for jpeg, but doesn't seem to make much difference) seems to produce VERY minor artifacting at best which takes zooming in past 100% to identify. YMMV however.

Sample size of 750 720x576 frames. Current PNG output is 390MB, JPEG at -q 1 is 35.3MB. So there IS a significant size difference at minimal quality loss.

With that said this is where my opinion and bias on this request comes in: JPEG is lossy and PNG is lossless. When dealing with the numerous conversion stages here (source video > png/jpg/etc frames > waifu2x processing and encoding to another set of png/jpg/etc frames > h264) especially with the focus of improving the quality of the source content, I would never trust a lossy intermediate format like jpg no matter how good of quality you can get it to produce. Disk space is cheap and for your average ~24 minute SD episode (again, based off my current working set of content at 720x576 source resolution, being processed up to 1440x1080) it should only be producing around ~130-150GB of frames both source and output.

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@cr08 I understood the problem afterwards.
DeadSix27/waifu2x-converter-cpp#114

Here was my conversation with waifu2x-converter-cpp's developer on this topic.
I might still try JPEG later.

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It's so sad that I've already written the code, but I git reset --hard'ed the thing.

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Added JPEG support in the newest version

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