Kostya's Boring Codec World

So far there’s not much to write about: I’ve dealt with the second most annoying thing (writing coefficients) and now my encoder can produce a valid stream of I- and P-frames. Probably it’s a good place to define a road map though.

First of all, there’s still the most annoying thing pending—in-loop filtering. And I can’t reuse that much code from the decoder since it was written back in the day when my knowledge of Rust was even less than now, so I have to partly rewrite some of the parts to make them fit my current approaches to the interfaces (that means a lot of DSP functions among other things). At least it can be disabled for now but I’ll have to return to it sooner or later.

Then there’s 4×4 intra prediction mode still waiting to be implemented. Again, I know how to pick the good enough prediction modes, it’s context-dependent coding of those modes that is going to be annoying.

Another thing missing is estimating the number of bits required to encode a single block. There are about five codebooks involved and those are selected depending on macroblock type, quantiser, coefficient block type (luma, chroma or luma DCs) and the global set index. I guess I’ll resort to gathering statistics for all possible coding modes and seeing if I can make some heuristic estimation out of it. And there’s still a task of selecting the best coding set for a slice…

After all that it will be mostly B-frame related things left to implement. I also need to make sure the muxer will write them out properly (for historical reasons in that case it mangles the timestamp to be last frame timestamp plus one). That’s not counting all possible enhancements like deciding the frame type for coding. Most likely I’ll be annoyed by it and keep the fixed coding order instead.

There are too many things to do and considering my pace it may keep me busy for a good part of the year—I mean a large part of a calender year, the current date is still February 24.

This entry was posted on Tuesday, April 18th, 2023 at 12:22 pm and is filed under rv4encfail. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.