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One of the interesting usage of AV1 was specifically for low bitrate calls, and software encoding was perfectly fine, even on mobile. With low enough resolutio

by Orphis 4mo ago

One of the interesting usage of AV1 was specifically for low bitrate calls, and software encoding was perfectly fine, even on mobile. With low enough resolution, framerate and bitrate, you can get a quality stream without significant encoding artifacts compared to any other codec. It is in production right now and has been for a while. The tradeoff CPU / bandwidth is quite advantageous in situations like this. And no, AV1 HW encoders cannot usually be used, they are not designed for a tight bitrate control or realtime communications like software encoding is usually.

ksec 4mo ago
Have you said this for Audio Codec I would have agreed. I do not know a single Smartphone Video Conferencing software that uses CPU encoding rather than hardware encoding. Neither WhatsApp or FaceTime, perhaps the largest of the two real time Video Call uses AV1.
- dannyw 4mo ago
  Yeah, no production or large scale VC system is running software AV1 encoders on smartphones. You will drain a full phone battery in 1-2 hours of calls. It just doesn’t make sense and will result in extraordinary power/battery drainage at best, or output that’s worse than hardware encoding. The only way you could get AV1 to software encode in realtime AND low latency on a mid-range Android chip is by disabling or skipping nearly all of the compression/encoding features that make it good at low bitrate.
  - Andrex 4mo ago
    So, status remains quo, the commons remain tragic, and glory to H.264 forever?
    - kergonath 4mo ago
      At least until a better codec has widespread enough hardware support, I think.
    - ksec 4mo ago
      > tragic H.264 isn't even that bad at all, if not the best depending on how you look at it. Our Internet bandwidth, both on the backend and front end on Mobile 5G is increasing with plenty more room to grow. While computation decoding and storage isn't. i.e If bandwidth is infinite and free, and we are only optimising for decoding power usage. H.264 wins in a lot of this scenario.
      - Orphis 4mo ago
        H264 is lacking a lot of features (behind patents) that are essential to real-time communications. It's available, but by far, the worst offender for call quality. Modern call technology will want to use temporal and spatial scaling which are not available in the profiles supported by most H264 encoders and decoders. Those tools are available for VP8 (temporal only), VP9 and AV1 and improve the quality of calls quite a lot when used right. I don't know about about the internals of H265 and H266 as those are also behind patents and no one wanted to touch them in the real-time conferencing space.
  - tecleandor 4mo ago
    > Yeah, no production or large scale VC system is running software AV1 encoders on smartphones. You will drain a full phone battery in 1-2 hours of calls. Yeah but, half jokingly, Zoom does that (draining the battery in an hour) already :P
- Orphis 4mo ago
  Google Meet can do it. You don't want the full conference with AV1, just use it for very low bitrate scenarios with a high packet loss possibly. Phones are a good target system. And I know this is quite opposite to expectations. It is a lot better to send a stable and visually ok stream with AV1 at 30KBps than fail to send a VP8 50KBps stream that is unusable anyway and is subject to twice as many packet lost than a lower bitrate solution. It is possible they use AV1 in other scenarios now, but I left the team a while back now and I haven't checked what they are now using under the hood.
jech 4mo ago
> One of the interesting usage of AV1 was specifically for low bitrate calls, and software encoding was perfectly fine, even on mobile. You really want hardware decoding on mobile, otherwise you end up with 40 minutes battery life. Fortunately, for typical videoconference resolutions, VP8 and H.264 are just fine. AV1 is nice to have, though, due to excellent support for synthetic content (screen sharing), and for scalable video coding (a much more elegant solution than simulcast, IMHO). In the world I live in, the general plan is to stick to VP8 and H.264 for the time being, and to skip to AV1 when it's universally available on mobile. I haven't seen any features of AV2 which would justify waiting for it.
- Orphis 4mo ago
  No, you do NOT want hardware anything on mobile if you are targeting smaller bitrate that are not that taxing on the CPU, when the conditions are otherwise so bad that the call would either drop or be unusable. HW encoders produce bad results at low bitrate. HW decoders usually have issues with the temporal encodings used and they may also just not accept those streams (a lot of test scenarios are movies, and the RTC tools are poorly supported). I worked on shipping it to Chromium, WebRTC and Google Meet many years ago and we had many publications about it: - https://blog.google/products-and-platforms/products/duo/4-new-google-duo-features-help-you-stay-connected/ https://blog.google/products-and-platforms/products/duo/4-ne... - https://webrtchacks.com/the-hidden-av1-gift-in-google-meet/ https://webrtchacks.com/the-hidden-av1-gift-in-google-meet/ The use case is not screensharing or a large conference room, but mainly a simpler talking face for a 1:1 chat, but with good quality as packet loss is then not as impactful on a 30KBps stream with AV1 than a 50KBps VP8 stream.
  - illiac786 4mo ago
    > HW encoders produce bad results at low bitrate. Is that poor implementation or is it inherently harder to implement in hw encoders?
    - defrost 4mo ago
      There's a few reasons, I suspect fixed resource depth might be factor in poor hardware single pass encoding ... What does limit them, though, is pseudo real time single pass pipelines. I see the best encoding results from two pass - one fast run to work out the easy compress and hard compress parts of a video and then a second pass to get the optimal results on a stream that's already got a budget in mind for each section through the advantage of foresight as to what's left to do.

by Orphis 4mo ago

ksec 4mo ago

Have you said this for Audio Codec I would have agreed. I do not know a single Smartphone Video Conferencing software that uses CPU encoding rather than hardware encoding. Neither WhatsApp or FaceTime, perhaps the largest of the two real time Video Call uses AV1.

dannyw 4mo ago
Yeah, no production or large scale VC system is running software AV1 encoders on smartphones. You will drain a full phone battery in 1-2 hours of calls. It just doesn’t make sense and will result in extraordinary power/battery drainage at best, or output that’s worse than hardware encoding. The only way you could get AV1 to software encode in realtime AND low latency on a mid-range Android chip is by disabling or skipping nearly all of the compression/encoding features that make it good at low bitrate.
- Andrex 4mo ago
  So, status remains quo, the commons remain tragic, and glory to H.264 forever?
  - kergonath 4mo ago
    At least until a better codec has widespread enough hardware support, I think.
  - ksec 4mo ago
    > tragic H.264 isn't even that bad at all, if not the best depending on how you look at it. Our Internet bandwidth, both on the backend and front end on Mobile 5G is increasing with plenty more room to grow. While computation decoding and storage isn't. i.e If bandwidth is infinite and free, and we are only optimising for decoding power usage. H.264 wins in a lot of this scenario.
    - Orphis 4mo ago
      H264 is lacking a lot of features (behind patents) that are essential to real-time communications. It's available, but by far, the worst offender for call quality. Modern call technology will want to use temporal and spatial scaling which are not available in the profiles supported by most H264 encoders and decoders. Those tools are available for VP8 (temporal only), VP9 and AV1 and improve the quality of calls quite a lot when used right. I don't know about about the internals of H265 and H266 as those are also behind patents and no one wanted to touch them in the real-time conferencing space.
- tecleandor 4mo ago
  > Yeah, no production or large scale VC system is running software AV1 encoders on smartphones. You will drain a full phone battery in 1-2 hours of calls. Yeah but, half jokingly, Zoom does that (draining the battery in an hour) already :P
Orphis 4mo ago
Google Meet can do it. You don't want the full conference with AV1, just use it for very low bitrate scenarios with a high packet loss possibly. Phones are a good target system. And I know this is quite opposite to expectations. It is a lot better to send a stable and visually ok stream with AV1 at 30KBps than fail to send a VP8 50KBps stream that is unusable anyway and is subject to twice as many packet lost than a lower bitrate solution. It is possible they use AV1 in other scenarios now, but I left the team a while back now and I haven't checked what they are now using under the hood.

jech 4mo ago

> One of the interesting usage of AV1 was specifically for low bitrate calls, and software encoding was perfectly fine, even on mobile. You really want hardware decoding on mobile, otherwise you end up with 40 minutes battery life. Fortunately, for typical videoconference resolutions, VP8 and H.264 are just fine. AV1 is nice to have, though, due to excellent support for synthetic content (screen sharing), and for scalable video coding (a much more elegant solution than simulcast, IMHO). In the world I live in, the general plan is to stick to VP8 and H.264 for the time being, and to skip to AV1 when it's universally available on mobile. I haven't seen any features of AV2 which would justify waiting for it.

Orphis 4mo ago
No, you do NOT want hardware anything on mobile if you are targeting smaller bitrate that are not that taxing on the CPU, when the conditions are otherwise so bad that the call would either drop or be unusable. HW encoders produce bad results at low bitrate. HW decoders usually have issues with the temporal encodings used and they may also just not accept those streams (a lot of test scenarios are movies, and the RTC tools are poorly supported). I worked on shipping it to Chromium, WebRTC and Google Meet many years ago and we had many publications about it: - https://blog.google/products-and-platforms/products/duo/4-new-google-duo-features-help-you-stay-connected/ https://blog.google/products-and-platforms/products/duo/4-ne... - https://webrtchacks.com/the-hidden-av1-gift-in-google-meet/ https://webrtchacks.com/the-hidden-av1-gift-in-google-meet/ The use case is not screensharing or a large conference room, but mainly a simpler talking face for a 1:1 chat, but with good quality as packet loss is then not as impactful on a 30KBps stream with AV1 than a 50KBps VP8 stream.
- illiac786 4mo ago
  > HW encoders produce bad results at low bitrate. Is that poor implementation or is it inherently harder to implement in hw encoders?
  - defrost 4mo ago
    There's a few reasons, I suspect fixed resource depth might be factor in poor hardware single pass encoding ... What does limit them, though, is pseudo real time single pass pipelines. I see the best encoding results from two pass - one fast run to work out the easy compress and hard compress parts of a video and then a second pass to get the optimal results on a stream that's already got a budget in mind for each section through the advantage of foresight as to what's left to do.