3 ms·

Youtube probably have stats on viewer-happyness vs bitrate. I would take a guess that a higher bitrate = longer loading times, and viewers care far more about

Youtube probably have stats on viewer-happyness vs bitrate. I would take a guess that a higher bitrate = longer loading times, and viewers care far more about an extra few second of buffering than they care about audio quality, especially when they don't have the original to compare to.

echoangle 2y ago
Couldn’t you do adaptive Bitrate and start streaming low-bitrate for a few seconds and then switch to higher quality once the video is already playing?
- mungoman2 2y ago
  Yes it's very possible to do this. Without seeking support it's trivial, just instruct the encoder to encode with a low bitrate for a few seconds and then increase it. To support seeking you could encode a low bitrate stream, and a high quality stream, and then a number of ramps between these. So when you seek you start with the low bitrate stream and then after a few time units go on the ramp to the high quality stream.
  - kccqzy 2y ago
    The stream is already being split into chunks (identified in the m3u8 file) so encoding tricks like this won't be necessary.
- KeplerBoy 2y ago
  pretty sure they already do this.
- supertrope 2y ago
  YouTube’s most common audio codecs Opus and AAC use variable bitrate (VBR) by default.
- deathanatos 2y ago
  While nothing that's been said here is inherently wrong per se, a sample YT page load is ~5s to DOMContentLoaded, and without counting the video content, transfers ~7 MiB worth of requests & ~95 requests for me, and visually, the entire page feels like it loads twice. (I thought it was redirecting, but the inspector says nope, that's a single page load.) … while yeah… a lower bitrate upfront might lower the required bandwidth and thus, latency, to get enough of a buffer to start playback … all the bloat on the page would be a better first port of call.
  - londons_explore 2y ago
    I assume most viewers will already have most of the youtube javascript warm in the cache... How much is loaded for a navigation from one video to the next?
jorvi 2y ago
The audio data is miniscule compared to the video data, and the size of it is tied to the video quality level. And everything is streamed in chunks. It'd only amount to milliseconds of extra buffering.
- cogman10 2y ago
  Not as insignificant as you might imagine, especially if you are talking about surround sound audio. With newer codecs, doing 4k with 2Mb/s isn't unheard of. For audio, on the other hand, 32 or 64kbps per channel isn't unheard of.
  - jorvi 2y ago
    At 1080p60, YouTube uses 12Mbps, and 251Kbps Opus or 192Kbps AAC. That's a factor 50 smaller. Insignificant.
    - out_of_protocol 2y ago
      251 is codec format ID. Real bitrate is around ~135 kbps
      - jorvi 2y ago
        Totally missed that, thanks!
    - cogman10 2y ago
      > At 1080p60, YouTube uses 12Mbps It does not. That's a recommended bitrate for a live streamer (Streamer -> youtube). Coming out of youtube, the numbers are quiet different. For example, a random 4k video I just pulled had a video bitrate of 4.5Mbps. A 720p video I pulled of a talking head had a 369kbps video stream. That is to say, a podcast style video is likely to have a nearly 50:50 split on audio/video.
      - jorvi 2y ago

echoangle 2y ago

Couldn’t you do adaptive Bitrate and start streaming low-bitrate for a few seconds and then switch to higher quality once the video is already playing?

mungoman2 2y ago
Yes it's very possible to do this. Without seeking support it's trivial, just instruct the encoder to encode with a low bitrate for a few seconds and then increase it. To support seeking you could encode a low bitrate stream, and a high quality stream, and then a number of ramps between these. So when you seek you start with the low bitrate stream and then after a few time units go on the ramp to the high quality stream.
- kccqzy 2y ago
  The stream is already being split into chunks (identified in the m3u8 file) so encoding tricks like this won't be necessary.
KeplerBoy 2y ago
pretty sure they already do this.
supertrope 2y ago
YouTube’s most common audio codecs Opus and AAC use variable bitrate (VBR) by default.
deathanatos 2y ago
While nothing that's been said here is inherently wrong per se, a sample YT page load is ~5s to DOMContentLoaded, and without counting the video content, transfers ~7 MiB worth of requests & ~95 requests for me, and visually, the entire page feels like it loads twice. (I thought it was redirecting, but the inspector says nope, that's a single page load.) … while yeah… a lower bitrate upfront might lower the required bandwidth and thus, latency, to get enough of a buffer to start playback … all the bloat on the page would be a better first port of call.
- londons_explore 2y ago
  I assume most viewers will already have most of the youtube javascript warm in the cache... How much is loaded for a navigation from one video to the next?

jorvi 2y ago

The audio data is miniscule compared to the video data, and the size of it is tied to the video quality level. And everything is streamed in chunks. It'd only amount to milliseconds of extra buffering.

cogman10 2y ago
Not as insignificant as you might imagine, especially if you are talking about surround sound audio. With newer codecs, doing 4k with 2Mb/s isn't unheard of. For audio, on the other hand, 32 or 64kbps per channel isn't unheard of.
- jorvi 2y ago
  At 1080p60, YouTube uses 12Mbps, and 251Kbps Opus or 192Kbps AAC. That's a factor 50 smaller. Insignificant.
  - out_of_protocol 2y ago
    251 is codec format ID. Real bitrate is around ~135 kbps
    - jorvi 2y ago
      Totally missed that, thanks!
  - cogman10 2y ago
    > At 1080p60, YouTube uses 12Mbps It does not. That's a recommended bitrate for a live streamer (Streamer -> youtube). Coming out of youtube, the numbers are quiet different. For example, a random 4k video I just pulled had a video bitrate of 4.5Mbps. A 720p video I pulled of a talking head had a 369kbps video stream. That is to say, a podcast style video is likely to have a nearly 50:50 split on audio/video.
    - jorvi 2y ago