The Music Streaming Quality Hoax
Recently over a dozen music streaming services have been launched in Australia. They offer millions of tracks through a relatively low-cost subscription. My interest is in services that can play through Android devices like my ASUS Transformer Prime tablet which I hook directly into my hi-fi to play music in my lounge-room. I’ve recently had a close look at Deezer and Spotify, and MOG just launched today through my Internet carrier Telstra/Bigpond.
The big selling feature now is ‘streaming quality’. Spotify just raised its claim to be able to deliver almost all of its music at 320 kbps, a claim matched by MOG. But how can an entire back-catalogue be instantly raised in quality? My curiosity was tweaked while I was listening through Spotify to the Ben Harper tracks “Gold to Me” and “Burn One Down” from his 1995 album “Fight For Your Mind”. I had just installed the newest version of Spotify for Android in the tablet which has settings for “extreme quality” for streaming and for downloading, which I presume to mean 320 kbps. But the tracks sounded quite flat.
I have the original CD, and played it. I had used it as a reference CD several years ago to select my NAD hi-fi gear and KEF speakers. What a difference! Even though the CD is not in a high-definition SACD format, the sound has great dynamic range, the percussion is clear and rich, and the voice is breathy and present. The downloaded tracks from Spotify, on the other hand, lacked the range, the clarity and especially the punch of the music. I could hear sibilance in the singing. The cymbals rasped and the bell in “Gold to Me” sounded like it came from a bicycle.
I then tried to comparatively ascertain the downloaded track quality by ripping the music from the CDs myself. I used Windows Media Player and created MP3 files of each song at 128 kbps, 256 kbps and 320 kbps. I would expect the stream to use a newer format that achieves better quality at the same bitrates. I then imported the ripped files into Spotify on my PC, synced that playlist to the tablet, and played it back at comparable volume through the hi-fi.
The ripped 320 kbps version was very close to the CD quality in clarity, but just fell short in terms of harmonic richness and punchiness. In my opinion, after repeated comparisons, the Spotify download was better than the 128 kbps rip, but not as good as the 256 kbps rip. Therefore I would subjectively place the Spotify version in the range of 160 – 192 kbps in quality.
What’s going on? I think we are being fooled. The music streaming services are probably claiming correctly that they are delivering 320 kbps of music data. But I don’t think they have gone back into their catalogues and re-sampled all the tracks from lossless CD quality (equivalent to 1411 kbps) sources. Instead, they have probably up-sampled the compressed music that they have, which only required computing power and extra storage. But you cannot add clarity and dynamic range once it has been removed.
Of course, it is not an issue for all music. Jangly guitar-driven rock and over-dubbed pop sound just fine at 128 kbps. I think there is a marketing opportunity for a streaming service to differentiate itself especially in its jazz, acoustic and classical genres to put out special releases that are re-sampled at higher bitrates. Even mobile playback will benefit from that.
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