[FFmpeg-user] How do bitrate, FPS, and speed interact?

[christina zou]

Hi,

I have a pretty simple question.

I am recording video via 'raspivid' and sending it to FFMPEG to stream to
the internet.

At the settings 750Kbps, 15FPS, 720P (specified in both raspivid and
FFMPEG) I get reliable performance.

If I bump the bitrate to 1Mbps in both raspivid and FFMPEG, then FFMPEG's
stderr tells me that it hits 1Mbps, but the speed is reported around 0.67x
and my FPS is ~10, 2/3 of my target FPS.

My CPU usage doesn't go above 25%, and my wifi is capable of at max 5Mbps
upload speed, far higher than the 1Mbps video bitrate I'm attempting.

I'm trying to understand what is happening when Ffmpeg manages to hit my
specified higher video bitrates, but at the sacrifice of FPS and speed. Is
this because my internet is too slow?

My command: http://vpaste.net/kl3Vi