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Can you recommend any resources for learning about video codecs?

the_only_law 5y ago
Not sure if this is what you’re looking for, but this popped up a while back: https://blog.tempus-ex.com/hello-video-codec/ https://blog.tempus-ex.com/hello-video-codec/
- nopenopenopeno 5y ago
  This is perfect! Thank you!
- astrange 5y ago
  This is vaguely okay but makes the common mistake of overemphasizing that codecs use an IDCT. That's just a component of intra-prediction, it isn't necessarily important or used, and in H.264+ it isn't even a real IDCT when it is used. It's a simpler transform that isn't mathematically accurate but is bit-exact, which is more important.
Sunspark 5y ago
doom9 has a lot of good discussion.
- nopenopenopeno 5y ago
  Now we’re talkin! Thank you!
- dylan604 5y ago
  I remember back in the day when doom9 was blocked at the corp firewall level because it had posts on how to circumvent things. Nevermind it was the unofficial support for things like AVISynth, x264, etc. Even the nascent days of ffmpeg were there. It took a lot of cajoling and back and forth with legal depts, but eventually, was allowed to be granted access on an individual basis I owe a lot of what was accomplished to folks like DG and the other troopers from the bad ol' days of VFW based apps. It was like monkeys throwing rocks at the space ships compared to whats now. Remember when 2 cores was fast? For the person up thread talking about learning things, I wish I was in that position today with them rather than 20 odd years ago where everyone was in the dark, and thank the heavens for sites like doom9 that shone lights in dark places!
  - nopenopenopeno 5y ago
    >For the person up thread talking about learning things, I wish I was in that position today with them rather than 20 odd years ago where everyone was in the dark Where would you start today? And what was being circumvented? Copyright protection?
    - dylan604 5y ago
      DeCSS was considered a very big no no if you worked for a company that did work for content owners. Doom9 had lots of info on how to use DeCSS, and so it was flagged by lots of corps. Where would I start today? That depends on your level of interest, and what you want to do. Are you wanting to learn things to do to stay hip and cool making videos for the socials, or are you wanting to do technical things to video for less prestigious ends? That's two different paths that intertwine, but different recommendations depending. That's not a rhetorical question, btw. I've been in both fields, and continue to work in both. There's lots of reading, and today watching videos, but the biggest thing will be the access to actually doing the things that weren't possible so freely 20 years ago. Try things, make mistakes, learn, do again.
      - nopenopenopeno 5y ago
        I am interested in using video compression to improve delivery of VR and AR content over the web. But, this can mean a lot of different things! I know there is a lot of opportunity for this, I have a lot of ideas, but my knowledge of video compression and video streaming is limited. There are some companies working on this, but it’s not a singular problem or solution. I expect it will end up being many categories of solutions. I usually like to learn about things from first principles so that I can then choose what to intentionally skip over, if that makes sense. I find the history is usually a good place to start, but it only goes so far with these more blackbox type topics like video compression.
        astrange 5y ago
        It's all made of inter prediction + intra prediction + residual coding. There's an evolution from JPEG -> MPEG2 -> MPEG4 part 2 (XviD) -> AVC -> HEVC… where it gets more complicated over time but that's still the structure. There's also alternative ideas like wavelets (JPEG2000) and many other minor silly ideas; almost all of them are bad and can be ignored. Which is not to say the MPEG codecs are perfect. ML people think they can do "ML video compression" which will be a black box; I think this might work but only because calling your video codec ML means you can make your codec 1TB instead of a few hundred KB.

Not sure if this is what you’re looking for, but this popped up a while back: https://blog.tempus-ex.com/hello-video-codec/ https://blog.tempus-ex.com/hello-video-codec/

nopenopenopeno 5y ago
This is perfect! Thank you!
astrange 5y ago
This is vaguely okay but makes the common mistake of overemphasizing that codecs use an IDCT. That's just a component of intra-prediction, it isn't necessarily important or used, and in H.264+ it isn't even a real IDCT when it is used. It's a simpler transform that isn't mathematically accurate but is bit-exact, which is more important.

Sunspark 5y ago

doom9 has a lot of good discussion.

nopenopenopeno 5y ago
Now we’re talkin! Thank you!
dylan604 5y ago
I remember back in the day when doom9 was blocked at the corp firewall level because it had posts on how to circumvent things. Nevermind it was the unofficial support for things like AVISynth, x264, etc. Even the nascent days of ffmpeg were there. It took a lot of cajoling and back and forth with legal depts, but eventually, was allowed to be granted access on an individual basis I owe a lot of what was accomplished to folks like DG and the other troopers from the bad ol' days of VFW based apps. It was like monkeys throwing rocks at the space ships compared to whats now. Remember when 2 cores was fast? For the person up thread talking about learning things, I wish I was in that position today with them rather than 20 odd years ago where everyone was in the dark, and thank the heavens for sites like doom9 that shone lights in dark places!
- nopenopenopeno 5y ago
  >For the person up thread talking about learning things, I wish I was in that position today with them rather than 20 odd years ago where everyone was in the dark Where would you start today? And what was being circumvented? Copyright protection?
  - dylan604 5y ago
    DeCSS was considered a very big no no if you worked for a company that did work for content owners. Doom9 had lots of info on how to use DeCSS, and so it was flagged by lots of corps. Where would I start today? That depends on your level of interest, and what you want to do. Are you wanting to learn things to do to stay hip and cool making videos for the socials, or are you wanting to do technical things to video for less prestigious ends? That's two different paths that intertwine, but different recommendations depending. That's not a rhetorical question, btw. I've been in both fields, and continue to work in both. There's lots of reading, and today watching videos, but the biggest thing will be the access to actually doing the things that weren't possible so freely 20 years ago. Try things, make mistakes, learn, do again.
    - nopenopenopeno 5y ago
      I am interested in using video compression to improve delivery of VR and AR content over the web. But, this can mean a lot of different things! I know there is a lot of opportunity for this, I have a lot of ideas, but my knowledge of video compression and video streaming is limited. There are some companies working on this, but it’s not a singular problem or solution. I expect it will end up being many categories of solutions. I usually like to learn about things from first principles so that I can then choose what to intentionally skip over, if that makes sense. I find the history is usually a good place to start, but it only goes so far with these more blackbox type topics like video compression.
      - astrange 5y ago
        It's all made of inter prediction + intra prediction + residual coding. There's an evolution from JPEG -> MPEG2 -> MPEG4 part 2 (XviD) -> AVC -> HEVC… where it gets more complicated over time but that's still the structure. There's also alternative ideas like wavelets (JPEG2000) and many other minor silly ideas; almost all of them are bad and can be ignored. Which is not to say the MPEG codecs are perfect. ML people think they can do "ML video compression" which will be a black box; I think this might work but only because calling your video codec ML means you can make your codec 1TB instead of a few hundred KB.