How do I extract audio from video?
Pulls the audio track out of a video, copying it without re-encoding when the format allows.
Extract audio from video with FFmpeg
Pulls the audio track out of a video, copying it without re-encoding when the format allows.
ffmpeg -i https://cdn.rendobar.com/assets/examples/sample.mp4 -vn -c:a copy out.m4a- Encode
- 44 ms
- Output
- 60.5 KB
- Cost
- $0.0014
- Result
- m4a
job_02d6b802c13b4e53
The part everyone gets wrong
-c:a copy extracts the existing audio stream byte for byte, so it is lossless and near-instant. It only works if the container you are writing to accepts that codec: AAC goes into .m4a, not .mp3. Reaching for MP3 forces a re-encode you did not need.
What the common version does
Re-encoding to MP3 loses quality and takes longer, when the source audio could have been copied out untouched.
ffmpeg -i https://cdn.rendobar.com/assets/examples/sample.mp4 -vn -c:a libmp3lame -b:a 192k out.mp3It succeeds, and that is the problem
It did not error. It produced 118.7 KB against the correct command's 60.5 KB, a 2.0x larger file. A pipeline would accept this silently.
job_8937fd28df5342d6
Frequently asked questions
What goes wrong most often?
-c:a copy extracts the existing audio stream byte for byte, so it is lossless and near-instant. It only works if the container you are writing to accepts that codec: AAC goes into .m4a, not .mp3. Reaching for MP3 forces a re-encode you did not need.
What happens if I get it wrong?
We ran the naive version too. It did not error. It produced 118.7 KB against the correct command's 60.5 KB, a 2.0x larger file. A pipeline would accept this silently.
Do I need FFmpeg installed?
Not with Rendobar. The command on this page ran through the API against a URL, with no local FFmpeg and no server. The job id below it is the job that produced these numbers.
More recipes, all measured
Extract a thumbnail from a video Grabs a single frame as a JPEG or PNG, seeking to the timestamp first so it is fast on long files. Export every frame as an image Writes each frame to a numbered image file, or samples at a fixed rate to keep the count manageable. Make a contact sheet from a video Samples frames across the video and lays them out in a grid as a single image. Convert MP4 to GIF with FFmpeg Turns a video into an animated GIF using a generated palette, which is the difference between a usable GIF and a muddy one.
Run this without installing FFmpeg
This exact command ran through the API against a URL.