Jump to content

Sign in to follow this  

Identifying the best AAC bitrate version of a YouTube title

Recommended Posts

Camera encoding noticeably poorer than YouTube encoding at same nominal bitrate

I was recently puzzled by the fact that subjectively the sound quality I could get from a camera recording made with the AAC sound codec at a nominal bitrate of 128kbps approx was not as good as the sound quality  from a YouTube file streaming with the same audio codec and at the same nominal audio bitrate. (To test the camera, a high quality stereo audio signal was fed to the external microphone socket, at an appropriate level, with the camera's automatic gain control disabled.)

I discovered from examining audio bitrate variations as the files were playing that my Panasonic Lumix DMC-G7 camera keeps the recording audio bitrate within a fairly narrow range whereas YouTube videos involve higher peaks in the audio bitrate. (The camera needs to process on the fly. Youtube encoding is an off-line process.) I felt the disparity had been explained.


YouTube practices regarding AAC audio bitrate

In my internet searches about YouTube bitrates I'd noticed that although these days the AAC audio stream for a 720p YouTube video is generally streamed at a nominal 128kbps there have been differences of opinion regarding what bitrates have been used in the last year or so, and also differences of opinion regarding the subjective quality of the AAC audio. See for example this thread on another forum:


 and this more recent thread:  https://www.reddit.com/r/youtube/comments/6a8a87/request_to_the_dev_team_on_youtube_we_can_tell/


Test upload [only in draft form, and unlisted]

In the last week I decided to upload my own very brief 1080p video file to YouTube, with a high audio quality sound stream (44.1kHz, 24-bit, LPCM), to see what YouTube would do with it. I found the results were quite interesting. For the highest resolution video version (1080p), YouTube compressed the sound to a nominal 128kbps AAC stream. However for a lesser video quality version (720p), YouTube compressed the sound to a nominal 192kbps AAC stream.

For a lot of music, a nominal 128kbps YouTube stream may sound reasonable enough. However I had chosen a demanding sound track, the FLAC version of a professional closely miked recording of a string quartet. The 192kbps version of this demanding music was definitely better sounding for my ears than the 128kbps version, and the video quality at 720p was quite adequate.


Firefox add-on

I've found a Firefox Browser add-on that allows the available audio codecs and nominal bitrates of a YouTube title to be examined. This could be used to help identify the best audio stream. Here is a link to the add-on: https://addons.mozilla.org/en-us/firefox/addon/youtube-video-and-audio-dow/

From some spot checking I've done, and as a general statement, it would appear that if a 192kbps AAC audio stream is available, it is usually associated with a 720p video stream, not a 1080p video stream.




Share this post

Link to post
Share on other sites

I've been searching for a convenient YouTube downloader that lists the audio codec and bitrate. This one looked useful: Gihosoft TubeGet (downloadable from  https://www.gihosoft.com/free-youtube-downloader.html?from=prod).   Use of this downloader confirms that it does indeed seem to be the case that the 720p version of a YouTube is typically the one labelled as having a 192kbps AAC stream (rather than a 128kbps AAC stream).

Regrettably, I have found that a YouTube file version labelled by TubeGet or other tools as having 192kbps AAC doesn't necessarily have such a stream when downloaded. This may be what was being referred to in the first link in my opening post where one of the contributors stated:

[–]willb3d 1 point 1 year ago 

Yes. Regardless of what tools you may use to examine current YouTube quality, you will find that as of early 2016 the M4A audio component in all MP4 videos has been reduced back down to 128kbps (with the 16kHz cutoff of high frequencies) - as it was circa 2012 or earlier. It is a marked regression in quality.

However, the quality of the Vorbis audio component in the WebM versions of the very same videos are at 192kbps (or possibly higher - only 192kbps has been confirmed, but at least that brings the cutoff up to 19kHz). There is a noticeable difference in fidelity.


The draft 1080p video file I uploaded to YouTube myself  recently currently appears privately on YouTube with a 720p video version and an associated audio stream that an analysis tool will show labelled as being 192kbps  AAC and by downloading I can confirm the audio is indeed at that approximate average  bitrate.

Something fishy is going on here. More investigation needed!

This is an important issue for me as I find that for listening to classical music a 192kbps AAC stream can be a distinct improvement over a 128kbps AAC stream. 


The AAC sound for the 720p version of the YouTube video below doesn't sound too bad to my ears. However despite being labelled by TubeGet and other tools as 192kbps AAC, playing the downloaded file with Cyberlink PowerDVD will reveal that the AAC stream peaks at about 160kbps and at times is around 110kbps.  It is not 192kbps AAC:-




Share this post

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Sign in to follow this  

  • Classifieds Statistics

    Currently Active Ads

    Total Sales (Since 2018)

    Total Sales Value (Last 14 Days)

    Total Ads Value (Since March 2020)
  • Recently Browsing   0 members

    No registered users viewing this page.

  • Similar Content

    • By Luc
      I'm honestly not a listener of music from my 'era', I know the majority here are though so to them I'd be thinking this might not be a thread for them. It's a DSOTM/Led Zep/Barnsey/Sabbath/Mrs Mills no go zone really. 
      But I also know there's a very big group of SNA'ers who live for new music and they chase it down all the time, be it Bandcamp tragics like me and @Soundscape the member formerly known as Dave O))) or @Viognier chasing down live performances around the world or @scuzzii and whatever his sidekick Hensa is called these days or @mikey d and a mid coast vibe or @Willco and his very cluey touch on stuff we don't know know about.
      @mrbuzzardstubble  is I think SNA's most widely esoteric music listener and I'm hoping he'll add the odd video link to some outstanding music.
      My initial contribution is a Bandcamp discovery via Spotify via Robert Glasper and I'd love to see him live. @Viognier had a chance to see him last year in Sydney but I'm not sure whether he was able to get to the small venue where he played.
      Look at the age of the musicians in this YT clip...I'm weeping at the talent inherent in this display of virtuosity.
    • By candyflip
      Here's a potted view of the recent Moorabbin Record Fair, on Sunday 1/3/2020 in Melbourne.
      I thought it most valuable for you, to cover entire collections of some artists - in this case for Part 1, it was 2 whole boxes of interesting Pink Floyd releases from one regular vendor. And then The Mac, The Church, The Doors, Hendrix and Cream in Part 2.
      Part 3 has The Beatles, and more, and they are coming soon.
      Hope you enjoy.   

    • By peacewise
      Well, this is my 1000th post so I thought I'd try to make it a little different.
      It's been a really cool time forumming here at sna, I've been abused, & insulted FAR FAR less than any other forum I frequent, so great job to our community here. I mean that sincerely & nicely, I know intimately how easy it is to get amped up forumming.

      Shame the darkness hid the subs bottom.
      There's a brief walk around my room. Nothing too special, say when compared to the uberness & expense of darthlaker or Alistair.
      My hifi brings me great joy every single day, for me it is about the music, though I love the units too.
      So if you're inclined post up a tube of your hifi.
      Merry Christmas all.
      Live peacefully and with wisdom.
      Alternatively read David Zindell to discover the story behind the title "Peacewise"

  • Create New...