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YouTube Audio Quality Bitrate Used For 360p, 480p, 720p, 1080p, 1440p, 2160p

YouTube Audio Quality Bitrate Used For 360p, 480p, 720p, 1080p, 1440p, 2160p

Posted Jul 8, 2015 by Nick Vogt
YouTube streams video and audio separately and the website player combines them on the fly. Due to this, the audio bitrate is not affected by video quality like in the past. The audio you hear during a YouTube video will usually be either 126 kbps AAC in an MP4 container or 155-165 kbps Opus in a WebM container, regardless of whether you're playing 360p, 1080p, or any other resolution. Changing video quality will not impact the audio stream.


MP4 vs WebM


YouTube recommends that uploads be in the MP4 video format with AAC audio. So where does WebM and Opus come from? YouTube will automatically encode a WebM/Opus version of a video once it becomes popular, and stream that format during playback whenever a person's browser supports it. How popular a video needs to be before it gets a WebM version is difficult to say. I have some 900-view videos that have WebM versions but other 1000-view ones that don't yet.

Learn more about WebM and Opus audio here.


How to Determine Bitrate


I created a YouTube video info tool that gives readable details on the streams YouTube has available for a given video, and allows you to download the individual audio streams for analysis. This tool works for most videos, but not VEVO or other copy-protected videos (if you get a blank screen or empty download that is probably why).

The info that the tool provides comes directly from Google Video. Enter a YouTube video URL and hit enter. The Adaptive Formats section contains the individual video and audio streams YouTube picks from during playback. The Stream Maps section contains complete video files with audio that can be downloaded directly from YouTube. These Stream Maps are usually what YouTube Downloaders access when you want to download a YouTube video, but are not used by the YouTube player.

Once a video or audio stream is downloaded from the Adaptive Formats section, you can use ffprobe (part of ffmpeg) to analyse the file and obtain the real bitrate, which may differ a little from what is listed in the bitrate section on the tool.


Analyzing Network Traffic


To make sure YouTube isn't streaming some other file than what is shown above, I decided to analyze network traffic to see just how many bits are really being transferred. I did this for both MP4 and WebM videos separately using Chrome and Firefox's Developer Tools. For more details on the http requests involved in a YouTube stream, please see this technical post.

MP4
I created a 2160p test video with 320 kbps AAC music. Since it is new it doesn't have a WebM version yet. After uploading to YouTube and allowing it time to process, I analyzed the network traffic during playback and found that it was 126.886 kbps audio/mp4, which matches up very closely with what is reported by ffprobe on the downloaded file from Adaptive Formats in the info tool.

WebM
I analyzed a music video that had enough views to have a WebM version. I found that is was playing 156.188 kbps audio/webm, which also matches up very closely to what ffprobe reports.


Legacy Audio Quality


YouTube didn't always have separate audio streams. In 2013 and earlier, YouTube would play a specific audio bitrate depending on the video resolution selected. For example: 240p would get 64 kbps MP3, 360p would get 128 kbps AAC, and 720p would get 192 kbps AAC. For a full list of the legacy bitrates that YouTube used, see these tables:

From July 2012 to some time in 2013, YouTube used these bitrates, as long as the originally-uploaded video had a high-enough bitrate or was lossless.

ResolutionAudio Bit RateCompression
Original192 kbpsAAC
1080p192 kbpsAAC
720p192 kbpsAAC
480p128 kbpsAAC
360p128 kbpsAAC
240p64 kbpsMP3

Prior to July 2012, YouTube used these audio qualities:

ResolutionAudio Bit RateCompression
Original152 kbpsAAC
1080p152 kbpsAAC
720p152 kbpsAAC
480p128 kbpsAAC
360p128 kbpsAAC
240p64 kbpsMP3

Prior to May 2011, YouTube used these audio qualities:

ResolutionAudio Bit RateCompression
1080p128 kbpsAAC
720p128 kbpsAAC
480p128 kbpsAAC
360p128 kbpsAAC
240p64 kbpsMP3

Prior to March 2011, YouTube used these audio qualities for several years:

ResolutionAudio Bit RateCompression
1080p128 kbpsAAC
720p128 kbpsAAC
480p96 kbpsAAC
360p96 kbpsAAC
240p64 kbpsMP3
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