Audio quality

Audio formats used by Audio Downloader:

  • WebM (Opus) unprocessed raw audio
  • Opus unprocessed raw audio
  • AAC (m4a) raw audio
  • Vorbis unprocessed raw audio
  • FLAC lossless compression
  • Mp3 VBR lossy compression:
    • Bitrate average: 245 kbit/s, Bitrate range: 220-260 kbit/s (Large mp3 file size)
    • Bitrate average: 190 kbit/s, Bitrate range: 170-210 kbit/s
    • Bitrate average: 175 kbit/s, Bitrate range: 150-195 kbit/s
    • Bitrate average: 165 kbit/s, Bitrate range: 140-185 kbit/s (Balanced mp3 file size)
    • Bitrate average: 130 kbit/s, Bitrate range: 120-150 kbit/s
    • Bitrate average: 115 kbit/s, Bitrate range: 100-130 kbit/s
    • Bitrate average: 100 kbit/s, Bitrate range: 080-120 kbit/s
    • Bitrate average: 085 kbit/s, Bitrate range: 070-105 kbit/s
    • Bitrate average: 065 kbit/s, Bitrate range: 045-085 kbit/s (Smallest mp3 file size)

Let’s analyze the output of youtube-dl -F https://www.youtube.com/watch?v=4KcQ90UbRsg command and focus only on audio formats. For this file the formats are:

Format code Extension Resolution note
249 webm audio only DASH audio 53k , opus @ 50k, 1.13MiB
250 webm audio only DASH audio 71k , opus @ 70k, 1.50MiB
140 m4a audio only DASH audio 130k , m4a_dash container, mp4a.40.2@128k, 2.94MiB
251 webm audio only DASH audio 138k , opus @160k, 2.98MiB
171 webm audio only DASH audio 144k , vorbis@128k, 2.95MiB
Opus format has the highest bitrate and in this case, has also the best audio quality. So, if your audio equipment supports Opus format you should stick with it. The other formats AAC and Vorbis are also good options as they also do not need to be transcoded. These audio formats are downloaded without any transcoding and thus preserves the quality intended by the uploader. The audio downloader also can store data in FLAC format which is lossless but, in this case, the resulted file size is very large. If you want best audio quality and your audio system works only with FLAC so you have no other choice than use it. Lastly, there is also mp3 where the user has the opportunity to choose the quality and thus the file size. For mp3 transcoded with a variable bit rate of 190 kbit/s, we obtain near-CD audio quality. We must keep in mind that, Opus format produces the same results for bitrates around 160 kbit/s. There is a very comprehensive study about these audio formats available here.