iHeartRadio is supposed to be streaming at 128kbps mp3. My DAC shows different.

[Brian Hall]

I haven't tried iHeartRadio in quite a while. I started it up on my Chromebook (Android app) playing a stream from a local radio station and the DAC shows 48 khz as expected.

I selected Cast to my Wiim Pro Plus and the DAC switched to showing 96 khz. I switched to a "custom" radio station based off of a group I like and the DAC switched to 44.1 khz.

This is with the Wiim Pro Plus optical out going to an Eversolo DAC-Z8.

Did iHeartRadio up their game a little or is the app lying to my DAC when casting?

The "custom" station just changed to another song and the DAC switched back to showing 96 khz. I waited till another song and that one switched back to 44.1 khz.

 

[amirm]

I have never seen anyone stream MP3 at higher sample rates than 44.1 kHz. I don't even know if the typical encoders support higher sample rates. So if you are seeing something different, resampling is going on.

 

[staticV3]

There are radio stations that stream at 96kHz and beyond.

It's possible that when using iHeartRadio plugged into a DAC via USB, the audio is sent through Android's default audio pipeline and is resampled to 48kHz.

But when casting to your WiiM, iHeartRadio may pass the station's audio stream to it directly, meaning that the sample rate may change between stations.

 

[Brian Hall]

It has to be their app or server doing something funny. I let a few more songs play and it would stay on 44.1 khz for a couple, play one at 96 khz and then back to 44.1 khz.

This was using their free streaming. I don't subscribe to it. It didn't sound terrible and it didn't sound great. I was just surprised to see those numbers on the Z8 display.

 

[Brian Hall]

There are radio stations that stream at 96kHz and beyond.

I did not know that. I hardly ever listen to actual radio stations.

It's possible that when using iHeartRadio plugged into a DAC via USB, the audio is sent through Android's default audio pipeline and is resampled to 48kHz.

Yes, I don't know of any app that bypasses the 48 khz resampling done by Android on Chromebooks.

But when casting to your WiiM, iHeartRadio may pass the station's audio stream to it directly, meaning that the sample rate may change between stations.

The regular station stayed at 96 khz. It was only when playing the generated playlist that it was switching between 44.1 and 96.

When I cast Spotify to the Wiim, it stays locked at 44.1. Casting Youtube music stays locked at 48 khz.

 

[staticV3]

I did not know that. I hardly ever listen to actual radio stations.



Yes, I don't know of any app that bypasses the 48 khz resampling done by Android on Chromebooks.



The regular station stayed at 96 khz. It was only when playing the generated playlist that it was switching between 44.1 and 96.

When I cast Spotify to the Wiim, it stays locked at 44.1. Casting Youtube music stays locked at 48 khz.

Unlike Spotify and YouTube Music, iHeartRadio's playlists may fall into the same category as Qobuz, Deezer, Apple Music, etc where each song is streamed at its original sample rate.

By streaming to your WiiM, you're then bypassing Android's Resample step, leading to that fluctuating sample rate.

 

[ZolaIII]

Standard MPEG-1 Audio Layer Iii is limited to up to 48 KHz (24 per chenel) and 320 KB per second.
So you either ain't receiving mp3 or device does upsampling on it's own. Opus is limited to 20 KHz per chenel but uses 32/24/16 bit sample packing depending on original complexity. AAC can go to 96 KHz and that's probably what you are receiving in this case. And that covers the Internet streaming radio lossy codecs and Opus is the best one.