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Review and Measurements of Chromecast Audio Digital Output

GGroch

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I have sold my last SqueezeBox network receiver last week for $90 ... a 10 years slice of my life gone ...
Yes, and you missed the peak resale market by about 5 years. For a couple of years after they were discontinued used units were selling for 3-5 times the original new retail price. Perhaps speculators drove some of this last minute CCA purchase frenzy.

The thing is, if they would add a line out to the Google Mini (which I expect them to do), it would solve the problem for all but a few of us DAC loving audiophiles. The Echo dot already has that.
 

D700

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Yeah, I think Amazon make actually emerge as the "interface" for a lot of this stuff. My informal personal checks at Christmas had shelves of Echo and Spot disappearing while looked like Google couldn't give their stuff away. The new line of Amazon stuff includes a lot of audio oriented components...how hard would it be to add an optical out to an Echo Show? Amazon seems willing to just make stuff, see what market likes then iterate for version 2. Plus, I like Alexa so far, seems better than Ok Google and Siri. What I really want is a Marantz network player like the NA6006 but smaller with a better screen.
 

DDF

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CCA is/was the only reasonably priced and easy method to get "bit-perfect" Spotify to an external DAC.
Unfortunately not from Android: Spotify transcodes from 320 OGG down to 256 AAC and isn't gapless. Keeps me using Tidal over BubbleUPnP Android: bit perfect and gapless, but uses Android as the stream source and not just control point (a bit of a battery muncher).

When I saw the posts here I checked Ontario and CCA was sold out at Best Buy, Staples, Amazon, Canada Computers... basically everywhere. Just bought one from red Deer Alberta via Kijiji! Already unobtanium.
 

gvl

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Unfortunately not from Android: Spotify transcodes from 320 OGG down to 256 AAC and isn't gapless.
True on gapless. I doubt Spotify actually transcodes OGG to AAC on the fly, CCA just pulls 256 AAC streams from Spotify servers, and the AAC streams are originally created from the same format as the OGG 320. This has nothing to do with Android. AAC is better compression so 256 AAC is about the same as 320 OGG quality wise if not better (AAC sounds better to my ears fwiw). Naturally both OGG and ACC are not bit-perfect to begin with, but at least with CCA you could get bit-perfect post unfolding, with gaps.
 

DDF

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True on gapless. I doubt Spotify actually transcodes OGG to AAC on the fly
Spotify support informed that audio sent to CCA is transcoded
https://community.spotify.com/t5/Li...-possible-Quality-to-Chromecast/idi-p/4523194

I've run blind level matched comparison of some material, between Tidal and Spotify, over CCA. Spotify often sounds a bit more muffled. Could be coincidence or situational to the files tested but I have no dog in the game so wasn't biased either way (actually, was biased towards Spotify if anything hoping that I could ditch the Tidal account), and this was before I knew about the transcoding. It sparked my info search.

Interestingly I saw a job opening at Spotify recently for a SW engineer with transcoding experience, to work on transcoding.
 

gvl

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Spotify support informed that audio sent to CCA is transcoded
https://community.spotify.com/t5/Li...-possible-Quality-to-Chromecast/idi-p/4523194

I've run blind level matched comparison of some material, between Tidal and Spotify, over CCA. Spotify often sounds a bit more muffled. Could be coincidence or situational to the files tested but I have no dog in the game so wasn't biased either way (actually, was biased towards Spotify if anything hoping that I could ditch the Tidal account), and this was before I knew about the transcoding. It sparked my info search.

Interestingly I saw a job opening at Spotify recently for a SW engineer with transcoding experience, to work on transcoding.
That is just someone's interpretation. AAC is just another Spotify distribution format for embeded clients and the web player. Tidal is lossless, it "should" sound better.
 

DDF

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That is just someone's interpretation. AAC is just another Spotify distribution format for embeded clients and the web player. Tidal is lossless, it "should" sound better.
You may be right that the person who wrote the post misinterpreted what they were told by Spotify support but I don't have any reason to think that. Spotify also have transcoding engineers. Based on these two pieces of info and what I heard, evidence is pointing towards them transcoding.

BTW I use Tidal premium (320kbs), not the lossless HiFi. Too rich for my blood!
 

DDF

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Transcoding on the fly for millions of clients would be super expensive.
If they have the resource overhead to handle it in their infrastructure, its cheap. It doesn't take much (we put it in phones 25 years ago). I would think it much cheaper than creating, storing and setting up routing for another copy of every single song. That would add up to ~ 30% more hard drives, which are probably by far the least reliable part of their infrastructure.
 

gvl

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If they have the resource overhead to handle it in their infrastructure, its cheap. It doesn't take much (we put it in phones 25 years ago). I would think it much cheaper than creating, storing and setting up routing for another copy of every single song. That would add up to ~ 30% more hard drives, which are probably by far the least reliable part of their infrastructure.
I disagree. Storage is cheap, processing power is not, just think about energy use. They may have a fallback strategy to transcode in cases when the format isn't available but I'd be very surprised if they didn't keep AAC encoded content ready to serve for the majority of albums created from masters or whatever they use for originals.
 

DDF

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I disagree. Storage is cheap, processing power is not, just think about energy use. They may have a fallback strategy to transcode in cases when the format isn't available but I'd be very surprised if they didn't keep AAC encoded content ready to serve for the majority of albums created from masters or whatever they use for originals.
I know through my work (the optical transmission between data centers) that storage isn't cheap compared to processing, its also much less reliable and a power hog (data centers are massive power sinks). These transcode algorithms are light weight, I think you'r exaggerating the resources required for them. I used to work professionally with coding, transcoding and IP data transmission of audio and my experience doesn't match what you're saying.

We're both speculating about how Spotify's infrastructure is set up but a few other tantalizing tidbits. Spotify moved its infrastructure to Google Cloud:
https://cloud.google.com/blog/produ...e-cloud-platform-to-power-data-infrastructure

Google Cloud supports transcoding:
https://cloud.google.com/solutions/..._campaign=resources&utm_content=resource_card

Edit: see page 295, https://books.google.com/books?id=d...age&q=spotify google cloud transcode?&f=false

Spotify uses transcoding
1547269074151.png
 

gvl

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Spotify for Artists

spotify.png


All I know that to convert from OGG Vorbis to AAC you need to first decompress to WAV and then run AAC compression on it. Sure, it won't cause a
blip on you home PC performance monitor but nevertheless it is a magnitude more computationally and memory space intensive task than simply sending the bytes as is. On a large scale you will need that many times more processing power to handle the transcoding.
 
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trl

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Just got one piece of Chromecast Audio and the mini-to-normal optical cable: $30. Cable is on stock, Chromecast Audio will get delivered during 7-11 of March.
 

DDF

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Transcoding is done once and resulting file stored, not transcoded in real time.Edit: I can’t find the article, will look tomorrow.
Please do. The text book I referenced clearly states that Spotify transcodes on the fly, it'll be good to get to the bottom of this. I'm surprised this info isnt readily available.
 

gvl

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Please do. The text book I referenced clearly states that Spotify transcodes on the fly, it'll be good to get to the bottom of this. I'm surprised this info isnt readily available.
The link I posted above clearly states that files are converted to all distribution formats up front from the original source.
 

DDF

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The link I posted above clearly states that files are converted to all distribution formats up front from the original source.
It says they are transcoded, not when, but encrypted before delivered to the platform. Lets see if we can get to the truth of it and not make it an argument
 
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