YouTube - HD video

[Nitreb]

When I watch a YouTube HD video (this for example: , in 1080 resolution), is it only the image that's HD, or also the soundtrack? If it's only the image, what's the soundtrack resolution, for example in the video referenced above?

 

[castleofargh]

the default audio format will be some AAC version, so you can have 96khz audio and fairly high bitrate, even 5.1 audio.
but there are 2 points to remember:
1/ it's a lossy codec, so whatever the sample rate equivalence, it doesn't get to be called high res as defined by Consumer Electronics Association and other big guys who come up with names so that they can monetize them.

Lossless audio that is capable of reproducing the full range of sound from recordings that have been mastered from better than CD quality music sources.

so better than 16/44 and lossless if we follow their decision.

2/ because anybody can upload anything, the resolution of the format container does not mean the music comes from at least that resolution. you can always take a 85kbps mp3 convert it to 24/96 wave and put it in a video at the highest resolution that's accepted. but the signal is still very much 85kbps mp3.
we get that kind of concern even from professional suppliers, so trusting your fellow youtube uploader to always provide the very best would be a little optimistic.

a quick recording in audacity suggests that there is no content after 16khz even in the highest resolution setting of this video. so you have to think low bitrate lossy format.

 

[bigshot]

Can we call it "audibly transparent"? If I remember correctly HD video uses AAC 256, which is audibly transparent.

 

[Don Hills]

I think it goes something like this:
If the video is in an MP4/AAC container, the highest audio bitrate is currently 128 kbps regardless of video resolution.
If the video is in a WEBM (VP9/OGG) container, the highest audio bitrate is currently 192 kbps.
At one time, this applied to 720 video resolution. Selecting a higher video resolution resulted in a lower audio bitrate. I haven't seen that recently. Apparently Youtube changed to the above max bitrates sometime in mid 2016. Previously, AAC audio had maxed at 192 kbps.

 

[pinnahertz]

When I watch a YouTube HD video (this for example: , in 1080 resolution), is it only the image that's HD, or also the soundtrack? If it's only the image, what's the soundtrack resolution, for example in the video referenced above?

The audio in that one is 16/44.1, AAC @ 125Kbps in an mp4 wrapper. Not even close to HD audio.

 

[widgets]

Does anything on youtube have better quality audio or have they designed it mainly for HD low(as possible) bandwidth video streams

 

[Nitreb]

The audio in that one is 16/44.1, AAC @ 125Kbps in an mp4 wrapper. Not even close to HD audio.

What I observe is that above a resolution of 480, only the image quality changes; the sound quality seems to stay the same.

 

[pinnahertz]

YouTube stopped varying audio quality with video quality sometime around 2013. It seems to be stuck at 128k AAC max, though files test at somewhat below that rate. Upload recommendations are of course higher as YouTube re-compresses everything.