Facts on Atmos streaming bitrates?

[JimHansonDC]

I'm not finding what I consider definitive answers. I read all I could find here and while trying to no be repetitive, I have some questions.

What are the known bitrates at which Tidal & Apple stream Atmos?
I saw 784 kbps which is pretty anemic.

Tidal talks about Master quality with 9216 kbps, but they don't say if that applies to Atmos and it appears not to (MQA issues aside). So what you can get is Uber-high quality stereo. Nice, but I want to listen to whichever service is sending an Atmos stream out the door at the highest rate. They all seem to want to hide that, which makes me believe they are sending it out at the screaming fast level I want.

The other part of this question is do we know if the stream-only Atmos mixes for the songs on these services are even encoded at bluray quality or are they not & just designed to be streamed out at the obviously much lower rates than physical media gives?

Any insight would be appreciated. I've read lots of educated guesses and tried to decipher the BS from the serices.

 

[JimHansonDC]

I agree it seems like a marketing ploy. I applaud the fact they are getting more Atmos mixes into play. And that they are a growing part of the streaming music universe. That is going to drive the demand for most major releases and back catalogs to get that treatment.

But they also have to deliver it in a format that is worthy of that additional effort to do the mixes. A stream at 784 k or whatever vs. a bluray delivering at 10 times that is ridiculous. But there are also costs for the streaming firms in infrastructure to do so and a fear of high bandwidth charges eventually from ISPs

Either way I am hopeful this is a good sign for the future, but doubtful they are delivering the real deal now.

 

[HaK77]

I conducted my own empirical test to determine the true average bitrates of Tidal's Atmos songs. I performed the test by setting up a Wi-Fi hotspot on my computer and monitored the data usage. The Chromecast, on which the songs were played, was connected to this hotspot, and no other devices were connected to it. I went through several songs, and here are the results.

Based on this, I draw the conclusion that the bitrates for Tidal's Atmos songs are not fixed. They likely operate dynamically depending on how data is distributed across different channels. These bitrates are calculated as averages from the overall data transmitted during playback.

Eric Clapton, "Lady in the Balcony," Kerry: Duration 5:00, data 29,678,964 bytes, average bitrate 791.44 kbps
Steven Wilson, "The Future Bites," Unself: Duration 1:09, data 22,548,296 bytes, average bitrate 2,615.59 kbps
James Brown, "I Got You (I Feel Good): Duration 2:48, data 31,876,924 bytes, average bitrate 1,517.19 kbps
Steven Wilson, "The Harmony Codex," What Life Brings: Duration 3:39, data 37,730,493 bytes, average bitrate 1,379.05 kbps

I hope to see someone else conducting similar tests to further explore and verify these findings.

 

[HomerJAU]

What are the known bitrates at which Tidal & Apple stream Atmos?
I saw 784 kbps which is pretty anemic.

The Dolby Media Encoder encodes Dolby Digital Plus (Atmos JOC) for streaming at maximum 1024kbps. Apple, Amazon and Tidal use 768kbps.

 

[HaK77]

While streaming Atmos content on my LG CX TV, I've observed the following information. It appears that the audio codec being used is E-AC-3. E-AC-3 is known to support up to 15 full-bandwidth audio channels at a maximum bitrate of 6.144 Mbit/s. For further reference, you can visit the Wikipedia page on Dolby Digital Plus: [Dolby Digital Plus - Wikipedia](https://en.wikipedia.org/wiki/Dolby_Digital_Plus).

As mentioned in my test results, I have observed bitrates higher than 768kbps.

 

[HomerJAU]

The Dolby Media Encoder encodes Dolby Digital Plus (Atmos JOC) for streaming at maximum 1024kbps and 48kHz.

DDPlus can support higher bitrates but Atmos JOC streaming is 768kbps.

Your TV is reporting the maximum supported by the current HDMI connection not the current transmitted data. Dolby Atmos cannot be encoded at 192kHz.

 

[HaK77]

Drawing from my own network usage data, it appears that Tidal may be employing a higher bitrate for streaming. I am interested in obtaining further information and understanding the rationale behind the 768kbps limitation.

 

[AYanguas]

How do you calculate empirically the encoded Atmos audio bitrate?

Here are some 'thoughts'. Please comment.

File Size in Bytes:
What file size? The complete M4A file? could containt metadata, cover image, etc. Or just the Audio track DD+/JOC

Streaming network bits:
I would calculate the Audio Track Bytes multiplied by 8 and adding the network protocol overhead. What network overhead? About 10-20%?

Additional Overhead:
Would the protocols between the Streaming Server and the Client App include additional overhead traffic? How much?

Final Calculation:
Average Bit rate = (Audio bits - overheads) / duration time

Is all this way?

 

[AYanguas]

Another question:

The DD+ encoded bitrate of maximum 768kbps, is referring only to the musical channel tracks?

Is the additional Atmos JOC metadata (objects and the like) included in this maximum bitrate?
If not, more metadata (good for Atmos), bigger file size.
If yes, more metadata, less room for the compressed music= more compression.

 

[HomerJAU]

The delivery bitrate includes metadata.

I updated MMH Atmos Helper recently to use the Dolby Media Encoder to encode what Dolby calls ‘DDP Atmos JOC for Blu-ray’ which has a maximum of 1664kbps. It would be nice if streaming services would provide encodes at this rate. Currently all Apple, Tidal and Amazon are all 768kbps.

 

[SeeMoreDigital]

I updated MMH Atmos Helper recently to now use the Dolby Media Encoder to encode what Dolby calls ‘DDP Atmos JOC for Blu-ray’ which has a maximum of 1664kbps.

Out of interest... With regard to Digital Plus encoding, does the Dolby Media Encoder offer just 5.1 with Atmos or can it offer 7.1 with Atmos?

And do any of the current streaming services offer 7.1 with Atmos?

 

[JediJoker]

Out of interest... With regard to Digital Plus encoding, does the Dolby Media Encoder offer just 5.1 with Atmos or can it offer 7.1 with Atmos?

And do any of the current streaming services offer 7.1 with Atmos?

DD+ is 5.1 only, even with JOC Atmos data. All streaming services are currently limited to 768kbps DD+JOC Atmos.

 

[HaK77]

DD+ is 5.1 only, even with JOC Atmos data. All streaming services are currently limited to 768kbps DD+JOC Atmos.

Where we can find that information above for example concerning Tidal? Source?

 

[JediJoker]

Where we can find that information above for example concerning Tidal? Source?

I'll rely on others for that confirmation. I don't subscribe to any of the Atmos streaming music services. As for the E-AC3 codec itself, it is capable of higher bitrates:

https://en.wikipedia.org/wiki/Dolby_Digital_Plus

 

[Owen Smith]

DD+ is 5.1 only, even with JOC Atmos data. All streaming services are currently limited to 768kbps DD+JOC Atmos.

DD+ can do up to 15.1. I don't know whether there's some restriction on that with JOC Atmos data, but without Atmos DD+ most certainly is not limited to 5.1.

 

[SeeMoreDigital]

DD+ is 5.1 only, even with JOC Atmos data. All streaming services are currently limited to 768kbps DD+JOC Atmos.

DD+ can do up to 15.1. I don't know whether there's some restriction on that with JOC Atmos data, but without Atmos DD+ most certainly is not limited to 5.1.

Indeed, I have quite a few 7.1 channel DD+ samples (there's even a channel checker from Dolby). I've even got a DD+ 7.1.4 or 6 (ie: with Atmos) somewhere.

My question however was: "do any of the current streaming services offer 7.1 with Atmos?", which JediJoker answered

 

[AYanguas]

Indeed, I have quite a few 7.1 channel DD+ samples (there's even a channel checker from Dolby). I've even got a DD+ 7.1.4 or 6 (ie: with Atmos) somewhere.

My question however was: "do any of the current streaming services offer 7.1 with Atmos?", which JediJoker answered

Tidal Atmos is:

Enhanced AC-3 with Joint Object Coding
768 kb/s
6 channels
L R C LFE Ls Rs
48.0 kHz

I cannot confirm the rest of streaming services.

 

[HaK77]

I use Tidal for streaming, and my primary method of playback is via Chromecast with Google TV 4K. As mentioned previously, my network tests have revealed a bitrate usage exceeding 768kbps. During my recent playback test, I examined the information displayed on my AVR (Audio-Video Receiver) app, which indicated a total of 8 channels on the input side. I'm continuing to investigate further for additional insights.

 

[HomerJAU]

Dolby Digital Atmos encodes JOC into 6 channels (5.1) for low bitrate and 8 (7.1) for high bitrate files. At 768kbps it uses 6 channels. At 1664kbps it uses 8 channels (TrueHD also uses 8). Either way Atmos can support 7.1 (up to 9.1.6). It’s just a slightly different way the encoder stores the audio information within the file structure.

Applications like MediaInfo and ffmpeg report this basic Dolby channel info (e.g 5.1 or 7.1) by looking at the file header but that’s just the internal storage structure. Each channel pair actually holds the Atmos JOC encoded representation of multiple channels, objects and metadata used by the decoder to recreate the original spatial mix during playback.

EDIT: So don’t sweat over the 5.1 or 7.1 info, it’s has no bearing on the actual internal Atmos mix. Lossy audio just need less data (encoded channels).

 

[AYanguas]

Dolby Digital Atmos encodes JOC into 6 channels (5.1) for low bitrate and 8 (7.1) for high bitrate files. At 768kbps it uses 6 channels. At 1664kbps it uses 8 channels (TrueHD also uses 8). Either way Atmos can support 7.1 (up to 9.1.6). It’s just a slightly different way the encoder stores the audio information within the file structure.

Applications like MediaInfo and ffmpeg report this basic Dolby channel info (e.g 5.1 or 7.1) by looking at the file header but that’s just the internal storage structure. Each channel pair actually holds the Atmos JOC encoded representation of multiple channels, objects and metadata used by the decoder to recreate the original spatial mix during playback.

EDIT: So don’t sweat over the 5.1 or 7.1 info, it’s has no bearing on the actual internal Atmos mix. Lossy audio just need less data (encoded channels).

I guess that the 5.1 or 7.1 channels alone would be played with all content, ignoring metadata, when using an AVR or processor that does not support Atmos or a sound option is selected without Atmos (if available). This explain the "all content is present in the mch 5.1/7.1" and the metadata decoding process "substract" content from the core mch and adds-it to the existing channels/speakers decoding both 'Atmos bed channels'' and 'Atmos objects'.

It is not related to the formats, but just commenting, out of curiosity, that sometimes it has happened to me that I couldn't get the "Dolby Atmos" appear on my AVR, and only the multichannel was played. After reseting AVR and/or re-initialize the player (Apple TV, Fire TV, etc) has solved the problem.