audio – supercurio's blog

ChromeCast Audio multi-speaker/multiroom first impressions

I just tried two Chromecast audio for the multiroom feature.
It's easy to setup and works well!

When plugging a pair of analog headphones on each Chromecast, CCAudio1 HP1 on left ear, CCAudio2 HP2 on right ear, matching volumes I wasn't able to discern a phase difference when playing a track on Google play music: great result.

It would be worth trying after a while to see if the Chromecast audio drift and how much: if the reference clocks are the DAC ones without compensation after the initial synchronization, I suppose it will drift at some point.

One limitation I experienced is that the volume was not matched anymore between both headphones after adjusting the group volume.

But still: pretty cool stuff, I think this platform has a promising future!

#supercurioBlog #Chromecast #audio #multiroom

In Album Chromecast audio multiroom first impressions

Source post on Google+

Confirmed: Chromecast audio analog output is 48kHz 16-bit today

I gave a hand to +FrAndroid +Manuel C. to explore the audio capabilities of the Chromecast audio.

Google confirmed what we found in measurements earlier: Chromecast audio resamples everything to 48 KHz 16-bit for both the optical and analog output.

– It is a poor default choice for audio since most material is sampled at 44.1 KHz.
– The resampler itself is not so great, introducing various distortion artifacts.
– The 16-bit output limitation is not welcome, including for 16-bit material since the volume control is software and digital.
– And it prevents playing 96 KHz 24-bit material without loss of quality.

Google say they are working on it, however they didn't adjust their marketing material announcing the support of 96 KHz 24-bit resolution which is rather unfortunate.

I have a lot more measurements and data than the graph +FrAndroid republished, would you like to see them?

#supercurioBlog #audio #measurements #chromecast

Test du Chromecast Audio, le parfait compagnon de vos oreilles – FrAndroid
Après avoir rendu intelligents les écrans les plus basiques avec son Chromecast, Google a souhaité aller plus loin cette année avec le Chromecast Audio, un

Source post on Google+

How most audio equipment reviews seem to happen

I wouldn't say reviewing headphones with a scientific approach and objective methods is an easy thing to do: It is not.
It doesn't mean it's impossible, by any means.

Today's article from +Engadget illustrates how it looks to me most audiophile equipment (or audio equipment altogether) is evaluated.
Heck, for ultra expensive audiophile stuff, broken is good enough!

At the point where function itself is optional, you can guess the importance given the the actual product performance…

Quoting:
"But the more I think about it, the more it doesn't matter."

#supercurioBlog #audio #critic

I didn’t listen to a pair of $55,000 headphones

Source post on Google+

Casting lossless audio to Chromecast

+Manuel C. is preparing a Chromecast audio review for +FrAndroid and came to me today to talk about that. I shared my impressions and told him that I didn't find the time yet to develop a mini app based on the SDK to stream lossless audio to it.

So he found this music player, which is one of the first app available able to do just that!
The screenshot shows the upload bandwidth which corresponds to 44100 Hz 16-bit PCM Stereo audio when playing a WAV file for a quick verification.

44100*16*2 = 1411200 bit/s = 172 kB/s: perfect!

The name is Shuttle Music Player, from SimpleCity, by +Tim Malseed

Free: https://play.google.com/store/apps/details?id=another.music.player
Pro: https://play.google.com/store/apps/details?id=com.simplecity.amp_pro

Notes:
– I noticed already a little bug concerning casting audio volume so be careful with that.
Cool and promising app nonetheless, highly recommended try!
– Keep in mind that the Chromecast Audio and Chromecast 2 currently upsample everything to 48 kHz with a non-optimal resampling algorithm. So there's some loss here unless you're streaming 48kHz/16-bit PCM.

Now I can prepare Chomecast Audio quality measurement, nice!

#supercurioBlog #audio #lossless #Chromecast

Source post on Google+

+Vincent Sergère just published an editorial on 24-bit and 192 KHz audio support on mobile on +FrAndroid

I contributed by suggesting a few comments 🙂

A recommended read!

#supercurioBlog #audio #quality

A-t-on réellement besoin de l’audio HD (24 bits / 192 KHz) sur les smartphones ? – FrAndroid
Nous testons actuellement le Marshall London, premier smartphone de la célèbre marque anglaise d’amplis. Il arbore une puce audio dédiée (Cirrus Logic WM82

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A few notes about +Ars Technica comments on +HTC One A9 Audio

There's also a 24-bit DSP on-board, which upscales audio to 24-bit, as well as 24-bit DAC.

Fact is you'll be hard pressed finding a DAC installed in a phone during at least the past 5 years that are not accepting 24-bit wording on their bus, with at least 24-bit fixed-point DSP & oversampling, then converting to analog in 24-bit as well (some in 32-bit now as well)

There's no such thing as 24-bit "upscaling"
Or if you wish, everything audio out here already does that with a simple integer multiplication, you just didn't know about it.
But it's just an arithmetic operation, it doesn't improve the quality in any way.

However, does the system preserves this resolution from the audio player API, through the software mixing and processing and eventually to the Linux audio driver, that's something else.

iPhones benefit in dynamic range from 24-bit audio, when playing 24-bit files or even with 16-bit at lower volumes thanks to the volume mixer, but not many Android devices do even since Lollipop that adds 32-bit floating point audio.

Concerning what the marketing material and PR people say, I learned to not trust any of it regarding audio, you can only rely on measurements, they'll say whatever buzzword – sometime in good faith with no correlation whatsoever with reality.

My advice, as usual: measurements 🙂
If you want to know how to do that for your next article: let me know, I'll show you.

#supercurioBlog #audio #quality #press #critic

HTC One A9 hands-on: A midrange smartphone that feels like a flagship | Ars Technica
A solid, aluminum unibody paired with decent internals and a nice display.

Source post on Google+

Professional audio definition requirements for Android 6

In order for a device to advertise itself as professional audio capable in a way that the +Google Play Store or an application can be aware of, it will have to perform with an analog round-trip latency of 20 ms maximum.
A target of below 10 ms is recommended.

To give you a comparison point, iPhone and iPad are in between 6 and 10ms (for years)
A target of below 10 ms is what's commonly described as a requirement for real-time instrument sound processing as well as virtual instrument synthesis.

This is a new effort at encouraging the development of a music and pro audio ecosystem around the Android platform:

Nothing Google tried worked so far and Apple devices enjoy a quasi exclusivity on this segment as a result.
The thing is: Google doesn't tell manufacturers how to reach those low latencies. Qualcomm, the leading SoC provider doesn't know either.

Samsung tried something with a dedicated SDK implementing a JACK Linux audio based solution – bypassing AudioFlinger apparently but with mixed results: devs reported buffer underruns.
In consequence, we've seen no progress.

That's why while this new definition is a laudable initiative, it might not make any difference.

PS: Anyone with a +Nexus 5X or 6P wants to try to measure their round-trip audio latency?

Excellent find in the latest CDD, thanks to +Android Police.

#supercurioBlog #audio #latency #API

Google Explains Requirements For ‘Professional Audio’ Devices In Android 6.0
Android has long had trouble with audio latency, which has made most music creation tools unworkable on the platform. Things were vastly improved in Androi… by Ryan Whitwam in Marshmallow 6.0, News

Source post on Google+

Chromecast audio first impressions

I just received my #Chromecast audio and couldn't resist trying it right away with headphones.

So it's perfectly capable of driving the 300 ohms +Sennheiser HD 650.
The "High Dynamic Range" seems to produce a higher quality with these headphones, the output level also gets several dB higher when activated.
(then at the maximum level, it gives a sound pressure well above the pain threshold, with surprisingly low distortion)
Subjectively it also sounds rather good, which is not the case for every equipment with the HD 650: with its mostly neutral frequency response and low distortion it becomes a lot easier to tell the difference.

A very crude quick test via lossily compressed test samples seem to indicate the presence of some resampling artifacts on 44.1kHz content, none for 48 kHz (needs verification)

Still, it could probably serve as cheap headphones DAC / amplifier for special uses for headphones notoriously difficult to drive, replacing favorably a few smartphones or laptops' audio output.

But please don't take my word on it quite yet, I'll test with more headphones / earphones and also complete measurements.

I might have to write some new code for that however in order to cast lossless audio – apps I found so far use lossy transcoding which is not necessary.

#supercurioBlog #audio

Source post on Google+

Published yesterday by +iFixit :Chromecast 2015 and Chromecast Audio teardowns

On the audio part, we learn about the CC Audio's DAC setup used to drive the analog output.

The stereo DAC is an AKM AK4430:
http://www.akm.com/akm/en/file/datasheet/AK4430ET.pdf
– Up to 192kHz / 24-Bit
– 128 times oversampling for 8-48 kHz, 64 times oversampling for 32-96 kHz, 32 times oversampling for 45-192 kHz.
– 2Vrms output with its own charge pump
– 104 dB Dynamic Range
– -91 dB THD+N
– -104 dB crosstalk

Those are fine specs by themselves, but Google decided to add a component in the output path, a +Texas Instruments DRV632 Line Driver:
http://www.ti.com/product/DRV632/technicaldocuments
http://www.ti.com/lit/ds/symlink/drv632.pdf
– 105 dB Dynamic Range / SNR
– 0.002% THD+N = -94 dB THD+N
– 2Vrms output with its own charge pump.
– -110 dB crosstalk at 1Vrms output

I'm not exactly sure why this second component is present since the DAC already outputs in 2Vrms, which is what you want for line-output
+Texas Instruments lists the DRV632 usages as:
– a way to adjust the output gain (but only via external resistors and not digital)
– line output protection
– short circuit protection
– DAC post-filter (typically as a low-pass)
Based on the DRV632 specs, it should not harm the audio quality.

With a current limit of 25 mA, it should also be capable of driving some small headphones (although it's not designed for that)

Measurements will tell more the actual performance of this analog combo.

About that, Google just notified me of my Chromecast audio's shipment, so I'll try just that after receiving it.

#supercurioBlog #Chromecast #audio #teardown

Chromecast 2015 Teardown – iFixit

Source post on Google+

+Engadget misguided when reviewing the Chromecast audio

In cons:
* Audio quality may not be up to par for discerning listeners

For anyone out there who's spent a decent amount of money on audio speakers, there's a chance that the hardware inside the Chromecast Audio won't be of high-enough quality for such a purchase to make sense.

So how +Engadget evaluated the audio quality: Maybe guessing from the price point or something?
As usual, it would be nice for the press to abstain rating the quality of things they have no idea how to evaluate.

I look forward receiving mine, and will try to find a way to actually measure its analog audio quality, also the digital one (mostly: to see if there's re-sampling involved)

#supercurioBlog #critic #audio

Chromecast Audio review: Give your old speakers a new brain
Google’s audio-only Chromecast won’t make sense for everyone, but for a certain kind of customer, it’ll be a no-brainer.

Source post on Google+