What is hypothetical reference decoder?

Hypothetical Reference Decoder is a hypothetical decoder model that specifies constraints on the variability of conforming network abstraction layer unit streams or conforming byte streams that an encoding process may produce.

What is buffer size video?

buffersize: The size of the main buffer. Once streaming data comes into the main buffer, it is immediately split into the audio and video buffers. The default size of the main buffer is 1.5MB for HD models, 3MB for XD models, and 6MB for 4K models.

What is VBR peak constrained?

Peak-constrained VBR is like unconstrained VBR in that it is confined to an average bit rate over the duration of the stream. In addition, peak-constrained VBR conforms to a peak buffer. This buffer is described using a peak bit rate and a peak buffer window.

What’s the difference between a VBV and an overflow buffer?

It’s a bit counter-intuitive but a VBV underflowsignals an encoder rate buffer overflow(video bitrate larger than the input rate) while a VBV overflowsignals an encoder rate buffer underflow(video bitrate lower than input the rate). For ffmpegthe bufsizeis the size of the buffer.

How many kbps can a VBV stream hold?

If you have a large buffer, like in your second example, you can tolerate a higher bitrate for a greater amount of time until the buffer overflows. VBV makes sure your bitrate is lowered before that happens. That’s why your stream can reach 800-900 kbps.

Why does VBV buffer run out when data comes in too slow?

If data is coming in too slow the buffer will run out and the playback will stall. It’s a bit counter-intuitive but a VBV underflowsignals an encoder rate buffer overflow(video bitrate larger than the input rate) while a VBV overflowsignals an encoder rate buffer underflow(video bitrate lower than input the rate).

What’s the relationship between VBV and maxrate?

Hence you can have only short “low bitrate” periods. VBV takes care of all this! It makes sure that the buffer will never overflow nor underflow, as that would cause playback errors. Maxrate specifies the maximum bitrate that the video can ever have. I think Maxrate is independent from the current buffer filling level, but I may be wrong…