Bug: Down- and Upsampling of FLAC Files in the signal chain with activated Mobile Transcode Rules Plugin

[ChristianNoc]

The Mobile Transcode Rules (v1.3.0) plugin cannot be used properly with FLAC files. There are several errors occurring simultaneously.

Testing Condition: Mobile Transcode Rules (v1.3.0) enabled.

FLAC audio file:
Hotel California
2863 kbps VBR, 24-bit, 96 kHz, FLC

LyrPlay displays:
FLAC, 48kHz, 24bit, 2836kbps
The DAC outputs 96kHz. OK, we already know that the LyrPlay displays of technical song data aren’t very reliable.

So it still looks quite OK (if you take the values from the DAC). LyrPlay displays some values. Maybe same issue as: #81 (comment)

Closer look to the signal chain:
However, what you only see upon closer analysis of the entire playback chain is the following:

1. The Mobile Transcode Rules (v1.3.0) plugin requests downsampling from the LMS server.

2. The server actually delivers a downsampled stream with activated Mobile Transcode Rules to the LyrPlay Client (just to remember the original FLAC Files is encoded in 24-bit, 96 kHz)
   Bitrate: 2863kb/s VBR (converted to 705kb/s FLAC)
   And that down conversion corresponds to the standard 44.1kHz at 16-bit.

3. LyrPlay then performs upsampling (!!) on the delivered 705kb/s data stream (as the DAC shows its upsampled again to the original value of 96kHz). To make matters worse, you cannot rely on the LyrPlay displays, which shows 48 kHz. But that is completely irrelevant at this point. First, downsampling is performed on the LMS server (apparently requested by the plugin) and then it is upsampled by LyrPlay again. That is a no-go for the sound quality and makes absolutely no sense.

With deactivated plug-in it’s just the unreliable display within LyrPlay.

[mtxmiller]

What do you have set in lyrplay settings for max sample rate?

I don’t think anything is Upsampling.

The transcode plugin allows you to transcode file at same bitrate with headers which allows seeking within a flac file - that’s all it does.

Now the display on interface is confusing — there is baseline what material UI displays and then there is what LYRPlay injects into material JavaScript - this isn’t super reliable.

So again what is being showed in settings view is more reliable true output of lyrplay - please check that vs using material UI output and confirm - if you have no sampling limit and mobile transcode you should get exact same output as file originally was.

[ChristianNoc]

Max. Sample rate is 192khz in LyrPlay.

The server shows that conversion messages also in the native HTML interface. I tried also to change settings in my costum convert file some years ago but fiddling around in that file is tiresome and for me it was not successful.

I am sure that the server does the downsampling when the server shows that message. Disabling the mobile Plugin and all is ok. But of course no seeking.

[ChristianNoc]

I just cross checked. That is the server view with the old classic interface. The server does a downsampling. For me it’s sure.

And even with 44.1khz and 16bit files. That’s weird.

Just cross checked again with the mobile plug-in deactivated. All is as it should be with no server side downsampling.