What video encoding format supports variable bit rate streaming (quality) and a SEEK function to skip segments?

Question

I'm looking for a Multiplatform video format that allows for a variable bit rate for streaming over high or low quality links, and also a seek function that allows a byte[] range offset (as in HTTP commands) to fetch a missing or lower than desired quality.

Answer 1

I think it is worth separating encoding and streaming to help the background.

Most streaming protocols will stream video contained in 'containers' e.g. MP4, WebM etc. The containers will include video tracks which can be encoded with different encoders, e.g. H.264, H.265, VP9 etc.

The term Variable bit rate is usually used to describe how the encoding is done - i.e. the encoder may compress or encode the video so it has variable quality and fixed bit rate or try to maintain a given quality level but with a variable bit rate.

I suspect what you may be more interested in is what is called Adaptive Bit Rate streaming - here the video is 'transcoded' into multiple copies, each with a different bit rate. The copies are all segmented at the same points, for example every two seconds.

A client can choose which bit rate to request for the next segment of the video, i.e. the next 2 second chunk, depending on its capabilities and on the network conditions at that time. Hence, the bit rate actually being streamed to the device can vary over time. See this answer for how you can view this in action in live examples: https://stackoverflow.com/a/42365034/334402

Assuming this meets your needs, then the two dominant ABR streaming formats at the moment are HLS and MPEG-DASH.

Traditionally HLS uses TS segments while DASH uses fragmented MP4. Both are now converging on CMAF, which means that the bulk of the media will be a single Multiplatform format, as you are looking for. There is a good overview of CMAF here at the time of writing: https://developer.apple.com/documentation/http_live_streaming/about_the_common_media_application_format_with_http_live_streaming

One caveat is that if your content is encrypted then, at the moment, different devices support different encryption modes so you may need to have separate HLS and DASH encrypted media for the medium term, until device support evolves over time.