OMG thank you so much, this is great help everyone!!!
some operations take a long time and some are quicker, i'm trying to hone in on
the ones that are quick and dirty, rather than re-encoding everything. It's so
hard to understand the documentation!!!
I'll try these commands and take notes on what works and what doesn't. Feel
free to let me know if you're interested in the results!
one thing i've been working with is that i'm doing concatenation at the same
time... so much obscure arcane procedure that you just find on the web and try
until it works.
And i was having troubles until i realized that the hard drives in the server I
was accessing were slowly dying off from overheating...
On Thu, 8 Oct 2020, Sean Greenslade wrote:
On Wed, Oct 07, 2020 at 11:19:36PM -0700, Carl
Gorringe wrote:
Hi Jake,
According to my notes...
To double the speed of a video:
$ ffmpeg -i input.mp4 -filter:v "setpts=0.5*PTS” output.mp4
Use -an to disable audio:
$ ffmpeg -i input.mp4 -filter:v "setpts=0.5*PTS" -an output.mp4
Use 0.333 instead of 0.5 for 3x speed. 0.05 for 20x.
cheers
-Carl
Some other tricks to squash file size:
If you don't need to do any seeking during playback and the scene is
mostly static, you can extend the keyframe interval with encoder
parameters. You can also tweak the quality target with crf (0 to 63,
higher is lower quality):
$ ffmpeg -i input.mp4 -an -filter:v "setpts=0.125*PTS" -c:v libx264
-x264-params "keyint=1000:crf=27" out.mkv
And if the contents of the video have truly static portions (like a
screencast, for example), you can use the "-tune animation" option.
For encoding speed, I think the libx264 encoder uses all threads by
default, but there is a -threads N option if it doesn't.
--Sean
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