Christian Feldmann - The Hypothetical Reference Decoder. Or: vbv-bitrate is not bitrate

Some of you might have already stumled on HRD parameters in h.264/AVC or h.265/HEVC. In the open source encoders x264 and x265 these can be enabled using the --vbv-bitrate and --vbv-bufsize options. Also the AV1 standard specifies a buffer model. While these buffer models were designed with fixed transmission lines and hardware limitations in mind, we see some use of them in modern applications for different reasons (like influencing the rate control). In this talk I would like to explain in depth what the HRD is and what the model describes. I want to explain why you must not think of bitrate when setting vbv-bitrate, what the connection to profiles/levels is and how these parameters influence and limit your encoder. Presented at Demuxed 2020.

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