How to set peak bitrate for a mp4 video using ffmpeg while encoding..?

[fahad]

Hi,

How do we set peak bitrate for mp4 video, using ffmpeg while encoding..?

The video bitrate is 600kbps, and the max bitrate is set as 800kbps, so after encoding the peak bitrate goes upto 1.3Mbps.. How do i limit this to 800kbps..??


Thanks,
Sanjay

[mvBarracuda]

Please post your current encoding line. The "-maxrate" parameter should actually work for this purpose, but I'm always encoding via the crf approach, so I've never tried if this actually works in reality.

[LoRd_MuldeR]

When you are using VBV, with VBVMaxRate and VBVBuffSize set, the encoder (e.g. x264) will make sure that no buffer underflows will occur.

You can check this later with a VBV Verifier tool. Of course you must configure your VBV Verifier tool with the same parameters (VBVMaxRate and VBVBuffSize) that were using while encoding.

Still, a simple so-called "Bitrate Viewer" tool may report "peak" bitrates above the VBVMaxrate, even for streams that are VBV compliant!

That's because the Bitrate Viewer only shows the "local" bitrate (average bitrate for a short time interval, like 1 second). It does not use the VBV model, so there's no relation to VBVMaxRate.

Or in other words: It's perfectly valid for VBV compliant streams to have "short" peak bitrates above VBVMaxRate (if the buffer fullness allowed it at that moment of time).