Two-pass encoding in ffmpeg
I will encode different videos uploaded by user asynchronously on my server. I saw this pos t, and according to that, here's how to encode the xy endcode:
ffmpeg -y -i input -c:v libx264 -preset medium -b:v 555k -pass 1 -c:a libfdk_aac -b:a 128k -f mp4 /dev/null && \
ffmpeg -i input -c:v libx264 -preset medium -b:v 555k -pass 2 -c:a libfdk_aac -b:a 128k output.mp4
I noticed the -pass 1 and -pass 2 flags. But I tried to encode the video by simply giving it the -pass 2 flag without the first encoding in the -pass 1 flag. Although I had this warning, it succeeded anyway:
The second pass has more frames than the 1st pass
So my concern is how will ffmpeg know which one is the first pass so it can do its pass 2 encoding? And since many videos will be downloaded at the same time, I cannot store them all in / dev / null if it replaces one with another. So how can I do this?
Your help and guidance would be much appreciated.
Thank.
Upadate
ffmpeg cmd:
ffmpeg -i input.mp4 -codec:v libx264 -tune zerolatency -profile:v main -preset medium -b:v 1500k -maxrate 1500k -bufsize 15000k -s hd720 -threads 0 -pass 1 -an -f mp4 /dev/null
ffmpeg -i input.mp4 -codec:v libx264 -tune zerolatency -profile:v main -preset medium -b:v 1000k -maxrate 1000k -bufsize 10000k -s hd720 -threads 0 -pass 2 -codec:a libfdk_aac -movflags +faststart output.mp4
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When using 2-pass encoding, the first pass will create files log
using a naming convention ffmpeg2pass-X
where X
is the stream number.
You can use the option -passlogfile
to set a custom prefix for your files. Example:
-passlogfile your_unique_video_id
This will create a file named your_unique_video_id-0.log
for stream 0.
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