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Sneaking Past Heavy-Handed Audio Compression on YouTube
Posted by
timothy
on Sun Jul 27, 2008 02:22 PM
from the sine-language-for-the-hearing dept.
from the sine-language-for-the-hearing dept.
niceone writes "Recently YouTube seems to have started applying extreme compression
to the audio of uploaded clips. This is the type of compressions used
by radio stations to make everything louder, but in this case applied
extremely badly. In quiet passages, breathing and shuffling become
overpoweringly loud. A gently plucked guitar chord becomes a distorted thud.
Listen to an example here. And here's what it could sound like — still not perfect, but a whole lot better. The
fixed version is thanks to a workaround proposed by
Sopranoguitar — the idea is to turn down the audio and mix in
a high frequency sine wave (I used 19kHz). The sine wave fools YouTube's
compressor into thinking that the file is at a uniform level (and does
not need the volume changing at all) but is filtered out by the encoding
process (so, no need to worry about deafening any dogs)."
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Wouldn't it be easier (Score:5, Insightful)
Re:Wouldn't it be easier (Score:4, Informative)
Wouldn't it be easier to set your gate [wikipedia.org] correctly?
That would apparently help, but only in cutting out the quiet scrapes and shuffles before the actual (attempt at) music starts. During that silent period, YouTube's encoder would be cranking up the gain so much that, when the first guitar pluck occured, it would still be a highly clipped thud. This workaround keeps them from adjusting the gain at all.
In other words, prefiltering your audio stream with a gate would quiet down the quiet parts, but would not prevent YouTube's encoder from fiddling with the gain.
Parent
Re:Wouldn't it be easier (Score:4, Informative)
During that silent period, YouTube's encoder would be cranking up the gain so much that, when the first guitar pluck occured, it would still be a highly clipped thud.
Well actually it really depends. It depends whether it's audio compression, or volume normalisation. If it's audio compression then things get amplified regardless of chronology, and therefore if you remove the ambient noise it won't get amplified to an audible hiss and it won't have a negative effect on anything else.
However what you were thinking about is "volume normalisation". In that case a quick change if volume would have the effect you described. I'm not sure which it is in this case but from the summary it looks like it's audio compression.
By the way, noise gating? There are more sophisticated things these days for that, like stuff based on STFTs and noise profiling.
Parent
Re:Wouldn't it be easier (Score:4, Interesting)
It still matters what they do. This kind of high compression is unsuitable for most material, yet they're insisting on it. Not only does it completely kill the dynamic range - imagine going to see a classical music concert and the entire concert is played at the exact same volume, no crescendos or decrescendos - that lack of dynamic range also dramatically quickens ear fatigue. What they're doing is great if they want people to stop listening (and therefore likely watching) YouTube videos as much. Otherwise, it's a really dumb idea.
Using a noise gate to solve YouTube's poor decision is not very realistic - that's trying to get thousands and thousands of different people to fix something caused by YouTube trying to solve what wasn't really much of a problem. What's more, noise gate + high compression leads to Charlie Brown Special kinds of voice tracks and very limited musical choices - e.g., in a classical concert, instead of the quiet parts being just as loud as the loud parts, some of the quiet parts will simply be cut to silence. Noise gate + high compression can be cute for a bit in dialogue, and when done to a particular instrument - but not every instrument in a song - you can get some cool effects from it, but it's shitty thing for YouTube to require of people. It may be enough to force some users away.
Parent
Update (Score:5, Informative)
I hope YouTube fix this soon.
Re:Update (Score:5, Interesting)
It looks to me like Google have done this on purpose to stop people uploading high quality audio with a still image. A lot of the music I've been listening too recently has been from youtube, I'm sure I'm not the only one...
Parent
Re:Update (Score:4, Informative)
Parent
Re: (Score:3, Informative)
Just sneak past the entire recompression process? (Score:5, Interesting)
Wouldn't another solution be to sneak past the entire recompression process by submitting a .flv video that meets YouTube's requirements to avoid recompression? Or would the compression on audio (not the same type of compression, the one this article is talking about) still be forced on these?
By the way to improve the trick, what you could do is detect the envelope of your sound, a modulate your 19 kHz sine with an envelope complementary so that the two envelopes would sum up to a flat line, so your 19 kHz envelope would be f(t) = 1 - original_sound_envelope(t).
Re: (Score:3, Informative)
"...Wouldn't another solution be to sneak past the entire recompression process by submitting a .flv video..."
Last time I submitted a video, about six to eight months ago, Youtube did not accept .flv or .swf formats, even though that is the format that they use to stream. Youtube wanted mpg, divx or mov formats. That sucked because my original was done in swf. First I had to convert the swf to divx which I uploaded to Youtube. Converting from swf to divx resulted in a big quality degradation. Youtube
Re: (Score:3, Insightful)
Standards (Score:5, Funny)
YouTube is just trying to enforce a standard level of quality to the content. Everyone expects crappy video with lots of compression artifacts, so the audio might as well follow suite.
but is filtered out by the encoding process (Score:3, Interesting)
Re: (Score:3, Funny)
Warning from ccalam in the second video (Score:5, Interesting)
The high quality version of the audio will have the 19 (or up to 22.1) kHz sine wave you choose to use in your video upload. So this is a trade-off of quality (high-quality = eek!) versus lack of unwanted range compression (low-quality = listenable, for lack of a better word).
FWIW, I can hear 19 kHz waves. So this trade-off affects me.
Re:Warning from ccalam in the second video (Score:4, Interesting)
FWIW, I can hear 19 kHz waves. So this trade-off affects me.
You won't hear 19 kHz much longer. Seriously, not because of this or any other particular factor (although there are many), but because everyone experiences upper-range hearing loss as they get older, and it starts at an astonishingly early age.
Parent
Teen Buzz/Mosquito Ringtone (Score:4, Interesting)
I have indeed heard of such deterioration on the Teen Buzz website (which is currently down for excessive bandwidth usage?) - but this page [wikipedia.org] describes it as well.
Those little annoying sine-wave sounds are also used by TV advertisers such as Kentucky Fried Chicken [youtube.com] to grab teens' attention if adults are not their market. (For the record, if you can't hear the tone, it sounds off when the KFC bucket shows up.)
Parent
KFC tone is 4825 kHz (Score:3, Informative)
Re: (Score:3, Interesting)
I worked with a guy once at a computer recycling place. He clearly had Asperger's, from the way his 'stories' were a list of facts delivered in a monotone, to his encyclopedic knowledge of model numbers and release years, to his inability to explain himself to anybody in charge. He could tell if a monitor was good
Nomalization standard? (Score:4, Interesting)
It surprises me after all these years, audio formats don't provide recording information about the dynamics of the waveform.
Cameras write EXIF information into JPEG files, why can't we have something similar for audio so we don't have to adjust the volume all the time?
You don't have to be an audiophile to appreciate good audio. I have a custom amp next to my computer into which I've plugged headphones. Find anyone with a pair of headphones, and you'll find an amp, too. Either that, or a deaf person who's been tortured by a bad Flash file.
Re:Nomalization standard? (Score:4, Informative)
There is, in MP3 at least. It's used by mp3gain:
http://mp3gain.sourceforge.net/faq.php [sourceforge.net]
However, not all audio players support it. I'm pretty sure the iPod doesn't, nor does iTunes. (For some reason iTunes does have a "normalise levels on all selected tunes" option but that works by decoding/re-encoding the audio, which is a lot slower because in addition to the audio analysis you have to re-encode the file and is likely to introduce further interference to the stream).
Having said that, I've only got a fourth gen ipod. For all I know, more recent models do make use of this tag and furthermore, for all I know if iTunes knows that it's being synced with an ipod which does support the tag then that's what it uses to adjust the gain.
Parent
Thank the iPhone (Score:3, Interesting)
I would guess they are doing this to better "service" handheld devices like the iPhone and upcoming Android devices that have limited dynamic range in their speakers.
Recording vs Processing (Score:4, Insightful)
Garbage In, Garbage Out.
The mics and electronics on most consumer camcorders (or that most people use with their Macs and PCs) are just plain crappy, and shouldn't be relied on for anything that you hope to distribute. And of course, some actual audio recording skills help too.
Re: (Score:3, Insightful)
Re:and who came up with it? (Score:5, Interesting)
Parent
Re:and who came up with it? (Score:5, Insightful)
I don't think YouTube is trying to run a loudness war, but rather trying to fix up a lot of amateurish recordings that are uploaded with bad audio. I can't tell you how many recordings on the net are either way to quiet (e.g. I can't hear speech even at max volume) or too loud and that change in mid-video (e.g. person walks away from or closer to mic). Despite their good intentions, though, it seems to have fallen prey to the "Clippy" effect.
What YouTube needs to do is have a little check-box on uploads that indicates whether to apply the auto-balance. And in case an uploader asks for no auto-balance when they really shouldn't (e.g. they think they know but don't) there should be a side link to listen to the auto-balanced version.
Parent
Re:and who came up with it? (Score:5, Funny)
But what if you move away from the mic to breathe ?
Chocolate Rain
*whoooosh*
Youtube makes my breathing loud again
Chocolate Rain
*whoooosh*
My eardrums are whimpering in pain
Parent
Re:and who came up with it? (Score:5, Funny)
Parent
Re:and who came up with it? (Score:5, Funny)
To YouTube videos? Sicko!
Parent
Re:and who came up with it? (Score:5, Funny)
To YouTube videos? Sicko!
What can I say? Unrehearsed rants into webcams really turn me on...
Parent
Re:and who came up with it? (Score:4, Informative)
they could have the volume knob (optionally) adjust to the appropriate volume for a given video.
They do, it's called compression.
Parent
Re:and who came up with it? (Score:5, Informative)
Louder is one thing, compression is another.
Compression can help bring out the faint natural harmonics in a sound, making it "warmer", not unlike an overdriven tube amp. These harmonics are like ear candy to most people, subliminally making the sound more enjoyable.
Radio stations do it for various reasons, one is it helps them sustain peak output power. Another is that the average radio is a cheap chinese gadget that sounds like liquid ass, so the compression actually helps with the sound quality on those devices. When you also consider where radio is often heard, e.g. malls, outdoor venues, cube offices, you realize these are all substandard listening environments where high dynamic range really means you lose half the sound, so the compression again helps with perceived quality by driving most of the content above the noise threshold.
There are plenty of good reasons for sound compression, but its use should be toggled by the user, and for the love of god, give it some sane thresholds! For most content, anything above 4x compression is overkill!
Parent
Re:and who came up with it? (Score:5, Informative)
Compression can help bring out the faint natural harmonics in a sound
Only a multiband compressor can do this, otherwise it just raises the level of all harmonics by the same amount.
If the one on YT is fooled by a 19khz sinewave then its single band compressor.
3:1 compression is usually considered the upper limit for practical purposes. Most people do prefer a small amount of compression.
Parent
Re:and who came up with it? (Score:5, Informative)
Parent
Re:and who came up with it? (Score:4, Interesting)
WPLJ 95.5 in NYC knew this very well back in the 70's they' use massive audio compression to keep the modulation index of the carrier at 95.5%... That needle just say there!
My station WDJF 107.9 Westport CT cared about audio quality. The MI followed the full amplitude of the source audio. Fed by 2 channels of full 15 khz equalized ma-bell-telco pairs. We sounded good! But PLJ was much much louder.
Parent
Re: (Score:3, Insightful)
Re: (Score:3, Interesting)
Are they making money with it? The first time I saw Youtube I thought "Yeah,the users will like it. But make money with it? It'll be pets.com all over again." If they use the traditional text ads they won't work as nobody will notice them,and putting ads before allowing the vid to play will just p*ss off the users and cause them to run away in droves. I know when I click on a weblink for a clip and some commercial starts playing I instantly close the tab. TV ads have gotten so bad I almost never watch anymo
Re: (Score:3, Informative)
You're not the only one wondering. Investors are as well. Found this story called Youtube Ads Underperforming [paidcontent.org]
Re:and who came up with it? (Score:4, Insightful)
Parent
Re:and who came up with it? (Score:5, Insightful)
Then hide the options. You don't protect the idiot by rubber-coating all the corners in the room, you protect them by putting the knives out of reach.
Parent
Re:and who came up with it? (Score:4, Insightful)
They could simply normalise the level, but if you have a speech with very low level and the guy drops the microphone in the middle, that one peak is so loud that will make the normalisation process useless.
But compression is such a complex and subjective issue that it should be performed by hand. I guess they have an automated process for that, and it doesn't have any intelligence, just steamrolls all the audio it finds, whether it's speech, music, or anything else.
Parent
Re: (Score:3, Insightful)
They need to allow a means of bypassing the compression, then.
Re:This hurts (Score:5, Informative)
Sure, how about the given example? One second is really all you need.
In the heavily compressed one, you hear an annoying hiss and the sound of the microphone being moved for the first few seconds.
In the non-heavily compressed one, you don't.
That's really the complete example without having to listen to the song. Really, the first few seconds are the best example, because Google is apparently amplifying almost complete silence to noise. The song part really doesn't help much. (Or at least, as much as I was willing to listen to it, which was only a few seconds.)
Parent
Re:This hurts (Score:5, Informative)
The worst examples I've seen have been videos of a lecture/speech, and while the main speaker has a microphone it also picks up sound from around the auditorium or lecture hall.
Normally this is fine as we have all become accustomed to faint background noise, with this extreme compression the faintest cough or shuffling in the audience sounds is as loud as the person speaking and is thus very distracting.
Considering most of the lectures I view are 30+ minutes long this really pisses me off.
Parent
Brevity Required (Score:5, Funny)
Can someone post an example I could possibly listen to for more than one second?
No
Parent
Re:Brevity Required (Score:5, Funny)
CLICK THUD TICK SSSS No FWWWW CLUNK CLICK
I'm sorry--what did you say?
- RG>
Parent
Re:Ruff ruff! (Score:4, Funny)
Ruff ruff rufff, and ruff rufff, you little bigoted ruff ruff ruffff.
Translation : I'm ultrasound-deaf, you insensitive clod!
Parent
Re:Lack of Choices (Score:4, Funny)
It would be nice if YouTube offered some choices, such as volume adjustment
Yeah, I mean, who on YouTube would even think of abusing that?
Parent
Choose better. (Score:3, Interesting)
Host your video somewhere else [archive.org], upload it in a high-quality format, and let the site make derivatives for you (including a Flash video and a player you can embed in your webpage if you insist on placating a proprietor). Some organizations do this daily and it works excellently. YouTube needs you more than you need YouTube.
Re: (Score:3, Informative)