Youtube Audio Reverse Engineering

[drgamble]

I tried to click on the link and this is what it told me:

drgamble, you do not have permission to access this page. This could be due to one of several reasons:

Your user account may not have sufficient privileges to access this page. Are you trying to edit someone else's post, access administrative features or some other privileged system?
If you are trying to post, the administrator may have disabled your account, or it may be awaiting

[matainais]

Exactly the same here too

[jackslab1]

same here.

[paul999]

Same here.

[tb-av]

Holy cow! You might want to warn people to turn their volume down before clicking those Youtube videos.

[brandondrury]

Hmmm. This shouldn't have showed up yet. The article isn't ready yet. Depending on how long my sessions are this weekend, it could be up on Saturday.

Holy cow! You might want to warn people to turn their volume down before clicking those Youtube videos.

I should probably think about this. Although 99% of all audio people complain about the loudness war, if you actually toss up a file with some dynamic range it blows people's heads off. It's another case where a nice loud mix has some very practical benefits. It's not that the clip is THAT loud. It's -8dB RMS, which is a hair under what most rock/metal records are these days.

Brandon

[tb-av]

Well let me put it this way. My headphones were sitting on my desk and plugged into my laptop at levels where I can listen to most anything on YT. When that first vid came on I had to grab the vol control. After I got it under control and actually tried to listen to the clips, I had to have my vol control on the "next to off" position. Every one of yours was that way but most other stuff on YT is not.

This is screen cap is a few notches up and absolutely as loud as I would want to listen that. Most things on YT I would be able to run maybe 3/4 or more.

Hmmm. This shouldn't have showed up yet.

The magic of the InterWeb

[onlinemusic]

Thanks for the research. Valuable stuff.

One way to quantitatively compare the results would be to download the resultant Youtube vids, extract the audio using MPEG Streamclip (free and awesome video/audio converter from Squared 5 - MPEG Streamclip video converter for Mac and Windows), then bring the audio into Cubase for analysis.

Another analytical tool is MediaInfo from MediaInfo
MediaInfo supplies technical and tag information about a video or audio file. You can just drag a file onto the GUI, and it will tell you more than you want to know about the codecs, compression parameters, bitrates, etc.

[Mackanov]

The probable reason your videos were the same size at 720p and 360p is because they were encoded at the same bit rate (for instance 2Mbps) instead of the same quality level. Sounds plausible?

Oh, what about 480p?

[Michial]

I PMd you and as I don't know how that works for sure on here I will mention that I am also TheMichGuff who commented on your latest video. I'm using Reaper and when I render I use a wave for Youtube but I don't actually remember whether it was 8bit or 16. Whether this is because of Moviemaker 5.6 or because of what Youtube excepts from me I don't know. I have tried both MP3s and wave and had the best sound with wave. I just mixed to what sounded good at the time to me, rendered to wave, added the wave to Moviemaker, did a quick scratch video and uploaded. When the weather gets nice again I will be concentrating on shooting better video. The weather here right now is -31C and w/ windchill -48.

[Michial]

Thankyou onlinemusic. I downloaded MediaInfo and it works as you said. According to it I was uploading 16 bit audio. I also discovered that I have dbpoweramp installed (Release13.5) and if you hover your cursor over the title of your video or audio file on your computer it displays some good info although the two are in disagreement over what version of MovieMaker was used. Anyways I'm interested to learn more about all this from everyone. Thanks in advance.

[untitled001]

I thinhk the beard looks good..

Now I'm going to read/watch the rest of the article.

[ChristopherW]

Surely a more definitive way to tell if YouTube is messing (significantly) with the audio would be to sample playback, time align and phase invert both the channels on the recording... If you were concerned about internal noise introduced in the analogue sampling on playback, you could always go and download the raw FLV from YouTube using one of the many ripper tools available, then extract the AAC soundtrack from the file with a tool like FLVExtract. Then you'd have a bitperfect AAC file, as (re)encoded by YouTube. Comparatively simple to drag into your DAW and compare that way.

YouTube *will* leave your audio stream alone, as it will your video stream, if you follow a very specific set of parameters and encode it in a particular way. However that only applies to the highest quality audio & video and it will still reencode - and transcode - for all other formats.


You've also omitted a couple of other quite important "things-to-check" with this article:

1: music with lots of bass frequency energy (and from what I've heard, lots of synthesised basslines) is absolutely MURDERED by YouTube's AAC codec. It really does it no favours whatsoever - bass freqs become an indistinct, rumbly mush even with 720p and 1080p uploads. However, music with acoustic / natural / amped bass guitar lines is equally effected. I have wondered for a while now whether they optimised their AAC codec to sacrifice bass and 10kHz+ quality to optimise encoding bitrates for the 1-10kHz bands (given that's where most acoustic energy seems to be is in the majority of crappy webcam and digital camera uploads using consumer gear).

Your audio clip (as heard on all of the test videos' soundtracks) was very bass-light, and unless you've watched quite a few videos (e.g. dubstep or Drum & Bass videos) I wouldn't have expected you to have already picked up on this. However it definitely merits further investigation.


2: another equally valid test would be to upload 20Hz-20kHz sine sweeps at a variety of bitrates. That way you could quickly hear if YouTube's audio reencoding was doing anything destructive to shifts in frequencies or sound in particular frequency bands.

[dudermn]

Good article, and thanks for taking the time to do that. Though a more impressive way would be to bleed through 'monitors', record, do a spectrum analist . Keep all the outputs identical and also don't move anything in the studio and record the comparisons. It could just be that youtube has a few standards for audio streaming, and should just be seen as a host that streams.

On to the good stuff.

1. Youtube now supports 4k video(, who cares.)
2. They use H.264/MPEG-4 AVC.
3. Audio is AAC at 44.1 khz with a range of 100kbps – 256kbps.
There are two articles that explain audio on youtube that may be useful, and may help discover a few more secrets :
1.> Bigger and Better: Encoding for YouTube 720p HD
2,> Approximate Youtube Bitrates » Ad Terras Per Aspera
8 . Youtube is believed not to support 1080p or 720p (here's an article explaining in detail the issue Youtube’s 1080p – Failure Depends on How You Look At It | Trevor*Greenfield)
And youtube does have it's own wikipedia page, which kinda helps to explain whats going on....(though it is just another way to advertise.)
Have a good day mates. And great beard.

[jazzroc]

Surely a more definitive way to tell if YouTube is messing (significantly) with the audio would be to sample playback, time align and phase invert both the channels on the recording... If you were concerned about internal noise introduced in the analogue sampling on playback, you could always go and download the raw FLV from YouTube using one of the many ripper tools available, then extract the AAC soundtrack from the file with a tool like FLVExtract. Then you'd have a bitperfect AAC file, as (re)encoded by YouTube. Comparatively simple to drag into your DAW and compare that way.
YouTube *will* leave your audio stream alone, as it will your video stream, if you follow a very specific set of parameters and encode it in a particular way. However that only applies to the highest quality audio & video and it will still reencode - and transcode - for all other formats.
You've also omitted a couple of other quite important "things-to-check" with this article:
1: music with lots of bass frequency energy (and from what I've heard, lots of synthesised basslines) is absolutely MURDERED by YouTube's AAC codec. It really does it no favours whatsoever - bass freqs become an indistinct, rumbly mush even with 720p and 1080p uploads. However, music with acoustic / natural / amped bass guitar lines is equally effected. I have wondered for a while now whether they optimised their AAC codec to sacrifice bass and 10kHz+ quality to optimise encoding bitrates for the 1-10kHz bands (given that's where most acoustic energy seems to be is in the majority of crappy webcam and digital camera uploads using consumer gear).
Your audio clip (as heard on all of the test videos' soundtracks) was very bass-light, and unless you've watched quite a few videos (e.g. dubstep or Drum & Bass videos) I wouldn't have expected you to have already picked up on this. However it definitely merits further investigation.
2: another equally valid test would be to upload 20Hz-20kHz sine sweeps at a variety of bitrates. That way you could quickly hear if YouTube's audio reencoding was doing anything destructive to shifts in frequencies or sound in particular frequency bands.

I whole heartedly endorse this.
Brandon, thanks for starting this enquiry.

[headrheum]

"Many video editing programs are really in love with this 48K sample rate thing. I can't imagine a single good reason why, but what else is new".

Have you heard about DVDs and BluRays and stuff?
They work with 48kHz Audio.
That's why.

[ChristopherW]

"Many video editing programs are really in love with this 48K sample rate thing. I can't imagine a single good reason why, but what else is new".

Have you heard about DVDs and BluRays and stuff?
They work with 48kHz Audio.
That's why.

As headrheum says, 48kH was also chosen I believe partially because it's a whole number samplerate - using 44.1kHz would lead to timesync drift and quantisation problems because the SMPTE clock would have to be constantly dividing by a fractional samplerate which is never desirable.

Why the music industry on its own only deals with 44.1kHz is beyond me, it's some kind of strange hangover from years gone by. 48kHz universally would make much more sense. Sony and Philips argued amongst themselves and came to a de facto standard which allows audio to 20kHz with a 2kHz transition band, but it still doesn't explain the .1kHz. It smacks to me somewhat of obstinate developer syndrome.

[UncleWaldo]

Brandon, two things:

1. You've got a Google Slap going on. Whenever I try to enter the site I get the, "This site is going to harm your computer" window. You might want to check that out.

2. After listening to all of your examples I've come to my own conclusion: crap in - crap out. You know what you're doing. We might here subtle differences in distortion but for the vast amount of listeners, they'll never catch it. Record it correctly in the first place and YouTube will provide a somewhat accurate playback of it.

[Chadfish]

I've noticed that before, anything 480p and above sounded "good" on YouTube. More recently I noticed that the "good" slot moved up to 720p, leaving the 480p stuff sounding dull. I hear no difference between 1080p and 720p. Most of my videos now go up ad 1080p, and youtube makes multiple versions and that's that. I gave up trying to annotate "Listen at 720p for better sound!" because it's a waste. People who care know to select a higher resolution.

I have a Vimeo account and the audio sounds great on whatever. If I want someone to hear a video I embed the vimeo version into Facebook or a forum. I still post everything to youtube because that's the popular way to spread your seed, but when I embed something on an audio forum, its Vimeo. I do mic shootouts, and even at it's best youtube still takes something away. For something as subtle as this shootout, you need the best available:
http://www.vimeo.com/19919137

[tb-av]

While I appreciate the work that had to go into making the test, it seems like an effort to create a solution for a problem that doesn't exist.

If you RTM, youtube tells you to use 256K encodes so why start with 320K? Why put it in their hands.

Is YouTube really your choice to deliver the nuances of your audio to your intended listeners? Hopefully not.

Can you get really good sounding audio on YouTube and get your point across. Absolutely. Just use their settings and playback at 720p or higher. Here is one example... http://www.youtube.com/watch?v=RT9PQgMtkDo

If you need better than that shouldn't you be considering something other than a free streaming service?