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this post was submitted on 26 Oct 2024
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Asklemmy
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if you’re planning on editing it, you can record in a very high bitrate and re-encode after the fact… yes, re-encoding looses some quality, however you’re likely to end up with a far better video if you record and 2x the h264 bitrate and then re-encode to your final h265 (or av1) bitrate than if you just record straight to h264 at your final bitrate
another note on this: lots of streaming stuff will say to use CBR (constant bitrate), which is true for streaming, however i think probably for re-encode VBR (variable bitrate) with multi-pass encode will give a good trade-off - CBR for live because the encoding software can’t predict what’s coming up, but when you have a known video it can change bitrate up and down because it knows when it’ll need higher bitrate
how does doing a 2pass work? I'm going to be honest, I just ignored that feature. Is it worth the extra hassle? And how much longer does it take? Also do I need to run ffmpeg twice for that? Or can I just put in an argument and it'll scan twice.
After typing all that out I realized that all this is probably easier to google/try than to ask you about it. Thanks for the info tho. I managed to get a video format where 15 minutes are 1GiB and watching it back I didn't notice any artifacts or burry parts in 1440p 60fps.
2 pass will encode a file once, and store a log of information about what it did… then on the 2nd pass it’ll use that information to better know when it should use more or less bitrate/keyframes - honestly i’m not too sure of the specifics here
now, it’s most often used to keep a file to a particular file size rather than increasing quality per se, but id say keeping a file to a particular size means you’re using the space that you have effectively
looks like with ffmpeg you do need to run it twice - there’s a log option
i mostly export from davinci resolve so i’m not too well versed in ffmpeg flags etc
doing a little more reading it seems the consensus is that spending more time on encoding (ie a higher preset) will likely give a better outcome than 2 pass unless you REALLY care about file size (like the file MUST be less than, but as close to 100mb)
I did a transcode with
-pass 1added, and it generated an empty txt file.