How do I convert mp4 to webm?
Encodes to VP9 and Opus in a WebM container, the royalty-free combination browsers accept.
Convert a video to WebM
Encodes to VP9 and Opus in a WebM container, the royalty-free combination browsers accept.
ffmpeg -i https://cdn.rendobar.com/assets/examples/sample.mp4 -c:v libvpx-vp9 -crf 32 -b:v 0 -c:a libopus -b:a 96k -t 5 out.webm- Encode
- 5208 ms
- Output
- 420.9 KB
- Cost
- $0.0067
- Result
- 1280x720
job_58374ee514aa4960
The part everyone gets wrong
-b:v 0 is mandatory for constant-quality VP9 and is the single most-forgotten flag in the codec. Leaving it out gives constrained quality that ignores most of what you asked for. VP9 is also slow: our own measurements had it at 5,347 ms where SVT-AV1 did the same job in 1,111 ms.
What the common version does
Without -b:v 0 the CRF value is treated as a ceiling on a constrained-bitrate encode rather than a pure quality target, which is not what CRF means elsewhere.
ffmpeg -i https://cdn.rendobar.com/assets/examples/sample.mp4 -c:v libvpx-vp9 -crf 32 -c:a libopus -b:a 96k -t 5 out.webmIt succeeds, and that is the problem
It did not error. It produced 420.9 KB against the correct command's 420.9 KB, a 1.0x smaller file. A pipeline would accept this silently.
job_7fd2c4d6ea724421
Frequently asked questions
What goes wrong most often?
-b:v 0 is mandatory for constant-quality VP9 and is the single most-forgotten flag in the codec. Leaving it out gives constrained quality that ignores most of what you asked for. VP9 is also slow: our own measurements had it at 5,347 ms where SVT-AV1 did the same job in 1,111 ms.
What happens if I get it wrong?
We ran the naive version too. It did not error. It produced 420.9 KB against the correct command's 420.9 KB, a 1.0x smaller 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
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. Extract audio from video with FFmpeg Pulls the audio track out of a video, copying it without re-encoding when the format allows. Trim a video without re-encoding Cuts a section out of a video by copying streams, which is effectively instant and lossless. Remove audio from a video Strips the audio track and copies the video untouched, so there is no quality loss and almost no work.
Run this without installing FFmpeg
This exact command ran through the API against a URL.