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YouTube quality selection

BobMaximus

BobMaximus

pfm Member
There's obviously a huge difference among the qualities of different YouTube videos. However, if I use the lower right cog, to change the quality of a given video (which usually has various settings, such as 480p & etc.), then I don't hear any difference among them. Why is this? I'm referring to the quality of the sound, rather than the detail in the video.
 
Video- from the Latin- I see.
Audio- from the Latin- I hear.

Why would changing the video resolution change the audio resolution.
 
The setting merely says "quality". But quality of what? If there's no video (ie. there's just a static picture), then that implies to me that it's the sound quality that's being referred to. What else could it refer to?
 
It definitely affects audio bitrate as well, I had a very nice example where one could clearly hear 240p vs 360p vs 480p vs 720p, but the video has since been taken down (copyright violation, I presume). The difference between 720p and 1080p is very small (might be nonexistent, I haven't checked the bitrates), but ie. 480p vs 720p is huge on some HQ-audio videos.
 
BobMaximus: The numbers - 480p, 720p etc. refer to the number of pixels in the vertical plane. "P" stands for progressive (as opposed to interlaced). You can google this.
 
jirij said:
It definitely affects audio bitrate as well, I had a very nice example where one could clearly hear 240p vs 360p vs 480p vs 720p, but the video has since been taken down (copyright violation, I presume). The difference between 720p and 1080p is very small (might be nonexistent, I haven't checked the bitrates), but ie. 480p vs 720p is huge on some HQ-audio videos.
Click to expand...
Okay, something has changed recently - 140p seems to have the same audio quality as 1080p on multiple videos I knew from before that happened. Few weeks ago (if I remember correctly), that was not the case.

edit: ok, there's still a difference (mainly stereo separation & lower bass frequencies) on some tracks (140p vs 1440p), but it's much, much less than what it used to be
 
narabdela: You are pushing it now, no?..

The OP asked why the audio quality doesn't change and I explain that it doesn't because that setting he is referring to only changes the video setting. Hence the 480p, 720p, 1080p numbers.
 
krenzler said:
narabdela: You are pushing it now, no?..

The OP asked why the audio quality doesn't change and I explain that it doesn't because that setting he is referring to only changes the video setting. Hence the 480p, 720p, 1080p numbers.
Click to expand...
Well, the short answer is: it might. Not because video quality is inherently tied to audio quality, but because encoders or players tend to use lower audio bitrate for a lower video bitrate, as a rule of thumb.

I queried the HTML5 file API for one youtube video using youtube-dl and I got more than I wanted:
Code: 
format code  extension  resolution note
140          m4a        audio only DASH audio  129k , m4a_dash container, aac  @128k (44100Hz), 2.66MiB
141          m4a        audio only DASH audio  255k , m4a_dash container, aac  @256k (44100Hz), 5.29MiB
160          mp4        256x144    DASH video  110k , avc1.4d400c, 12fps, video only, 2.26MiB
133          mp4        426x240    DASH video  253k , avc1.4d4015, 24fps, video only, 5.07MiB
134          mp4        640x360    DASH video  613k , avc1.4d401e, 24fps, video only, 11.48MiB
135          mp4        854x480    DASH video 1125k , avc1.4d401e, 24fps, video only, 21.69MiB
136          mp4        1280x720   DASH video 2265k , avc1.4d401f, 24fps, video only, 42.20MiB
137          mp4        1920x1080  DASH video 4163k , avc1.640028, 24fps, video only, 80.71MiB
17           3gp        176x144    small ,  mp4a.40.2, mp4v.20.3
36           3gp        320x240    small ,  mp4a.40.2, mp4v.20.3
5            flv        400x240    small 
43           webm       640x360    medium ,  vorbis, vp8.0
18           mp4        640x360    medium ,  mp4a.40.2, avc1.42001E
22           mp4        1280x720   hd720 ,  mp4a.40.2, avc1.64001F (best)
So the player can not only pick whatever audio it thinks it's appropriate for a given video bitrate, but in some cases, it doesn't have a choice (ie. webm) unless it's really smart and ignores the vorbis track, using a separately-downloaded audio-only track.

So despite recent changes, "use high video bitrate to get best audio quality" still (generally) applies.
 
Phew, I thought I was going mad because, on my desktop system (MF V90 DAC/amp and MA Radius 90 speakers), I thought the difference in quality was very clear. I would have found it embarrassing if if it was all in my head 'cos the numbers were larger! I can hear minimal difference from 480 to 720, but up to that it is very clear.
 
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