Playback Screen Data

Hi,

Could someone please help with the following question regarding data shown on the Playback Screen;

Playback_Screen.JPG
For Information this track is a 24 bit 96 kHz .WAV file.

Referring to values 32 bit, 44.1 kHz, 0 kbps for example.

Are these actual/measured values or read from tag files ?

  1. bit
    I can have 16, 24, & 32 bit shown, what does this signify and where in the Audio Chain ?
    For example I can play some 24 bit music that shows as 24 bit or 32 bit on the screen.

  2. Frequency
    This is OK, I see this is always accurate value.
    However is this actual/measured value or read from file tag ?

  3. bitrate
    This is often 0. For example with 16 bit 44.1 kHz. So why does this not show 1411 kbps
    It seems to work more accurately with Compressed files (e.g. MP3).
    Can someone explain what and when this value shows non zero values ?

Many Thanks in Advance, Kevin

Hi Kevin

I’m pretty sure all these values are calculated or at least measured from the file, and accurate for flac and mp3, but not accurate for other file formats like aiff and wav. It’s actually pretty hard to tag wav files with anything standard, so the depth, frequency and bitrate info is almost certainly (incorrectly) calculated for those.

If you play a lossy variable bitrate (vbr) mp3 volumio will show the recorded bitrate changing. Eg, the ‘lame’ mp3 codec encodes those files variablly to improve quality of recording but maintaining file size advantages ie more compression when there more silence in the frequencies and less when there is more going on. Volumio seems to take a snapshot periodically and reports that. Eg a vbr ‘5’ mp3 file will hover around the 160 - 220 kbps bitrate range.
For lossy constant bitrate (cbr) mp3 tracks it seems to accurately report the recorded depth frequency and bit rate eg 24, 44100, 320.

For lossless flac tracks at any depth and frquency again it seems to be accurately measure and report bitrate so a 24bit 192000 file hovers around 4608 Mbps. Flac only variably encodes and ‘compresses’ silence which accounts for the variability in bitrate. (This is a gross oversimplification of how flac works!)

Don’t forget that the decoding codec for any format will be gathering this information accurately in order to decode the files and output the music. Just like a car engine firing on all cylinders to turn the crankshaft and the wheels. Reporting the speed you are travelling at accurately, to the speedometer is another matter entirely.

Thanks for that Ian,

I will therefore concentrate on FLAC & MP3 for now.

FLAC
My experience with some tests today is that bit depth and Frequency are correctly displayed but for the bit rate values I am not sure what is going on
-.FLAC file 16bit, 44.1kHz, 1411 kbps ===== Volumio UI - 16bit, 44.1kHz, 475 kbps
-.FLAC file 24bit, 96.0kHz, 4608 kbps ===== Volumio UI - 24bit, 96.0kHz, 917 kbps

So my question is why is bit rate significantly different ? (e.g. 1411 vs 475)

MP3
I get good correlation with Frequency and BitRate, all my MP3 recordings are 44.1Khz (some varied Bitrates)
However Volumio UI always shows 24 bit.
Surely 44.1kHz recordings should be 16 bit :open_mouth:

Why would 24 bit be shown as bit depth for MP3 files @ 44.1 kHz ?

Many Thanks in Advance, Kevin

This isn’t an exact science Kevin. I have foobar 2000, on one of my windows machines which is pretty much the gold standard in terms of windows music players and gives a lot of data on files, both as they play and from the file.

Here’s a vbr mp3
Duration : 4:36.827 (12 208 056 samples)
Sample rate : 44100 Hz
Channels : 2
Bitrate : 212 kbps
Codec : MP3
Codec profile : MP3 VBR V2
Encoding : lossy
Tool : LAME3.90
Tag type : id3v2.3|id3v1

As it plays the actual bitrate displayed changes - Note no bit depth, his is common to all mp3’s - So that might be why volumio doesn’t report it correctly - if the decoding codec in foobar isn’t reporting it I doubt anything will.

And here’s a 24/192 FLAC

Duration : 3:52.328 (44 606 977 samples)
Sample rate : 192000 Hz
Channels : 2
Bits per sample : 24
Bitrate : 4872 kbps
Codec : FLAC
Encoding : lossless
Tool : reference libFLAC 1.2.1 20070917
Embedded cuesheet : no
Audio MD5 : 8E7DEB1DD67F6F1FF52B97723B0EAFF7

It won’t play the aiff files I have.

Foobar is freeware for windows so might be worth a download. Also its worth repeating that what is being reported is not necessarily a direct reflection of what’s being played. My DAC only has 4 lights 32, 44.1- 48, 88.2- 96 & 192. And no bit depth light, yet will play pretty much anything the spdif converter sends it and displays a signal lock light when it does so.

+1 to investigate better file format/tech details on the playback screen. Adding the file format would be really nice (FLAC/MP3 etc.), and would love to see more accurate sample rate/bit depth info!