My music library consists of a mix of lossy and lossless audio files and I’ve noticed that if I play a lossy format on cellular data, it transcodes it again from MP3 to Opus. This is a bad transcode. It is fairly well known that transcoding lossy to lossy file formats leads to generation loss and degredation of audio quality (https://en.wikipedia.org/wiki/Generation_loss).
There needs to be an option somewhere to only transcode lossless file formats like wav, flac, and alac. MP3s should be left untouched.
I suppose there’s always a balance between file size and quality when it comes to mobile streaming. As for re-encoding your original files, you might want to read about Opus and transparency.
I know that Opus is transparent at lower bit rates, but that doesn’t eliminate the fact that its a bad/lossy transcode. I think it would be totally reasonable to have an option called. “Transcode Lossless Only” or something to that effect.
I understand what is happening and how to stop it, but it doesn’t seem like anyone understands the problem here. This shouldn’t be happening in the first place. There is no reason to ever transcode a lossy MP3 to another format. You are losing data when you perform this transcode. It is totally reasonable to want FLACs to be encoded in Opus at 128-160kbps and to not encode lossy MP3s. I can do what you’re suggesting as a temporary measure, but this doesn’t actually solve the problem that plexamp is allowing bad/lossy transcodes to occur.
It would take you guys only a few minutes of google searching to see that lossy to lossy transcoding should NEVER occur. You shouldn’t even need to change a setting. This just shouldn’t occur and if you have some weird excuse for ever wanting a lossy-lossy transcode then it should pop up with a warning letting you know that you will be unnecessarily losing out on even more audio quality.
EDIT: Expanding on my point, it’s also important to note that different formats are transparent at different bitrates. The current settings only allow you to pick a SINGLE bitrate threshold. It doesn’t let you pick to only use Opus for FLACs and leave MP3’s alone. Let’s say I have an MP3 encoded at 320 and a Flac encoded at like 765kbps. If I change my settings to 320 to ensure that the mp3 isn’t converted, I will now be unnecessarily converting FLAC’s to Opus 320 which is going to take up more than twice the bandwidth when Opus is already transparent at 128-160.
Sorry, but in this instance you are misunderstanding.
There is a difference between the threshold at which a transcode occurs (the Music Quality->Cellular setting) and the bitrate of the transcode once it occurs (the Advanced->Conversion Bitrate) setting.
If you have, for example, the Cellular setting set to 320kbps and the Conversion Bitrate setting at 128kbps then you will achieve what you want. FLAC files over 320kbps will be transcoded to Opus 128kbps and mp3 files at or under 320kbps will not be transcoded.
Oh wow I didn’t even notice there was an advanced conversion bitrate setting. Everything works great now with the settings changed to reflect that. Thank you so much for the help.
I think my point still stands though that bad transcodes shouldn’t actually be possible and maybe the conversion bitrate should not be buried in the advanced section and should be moved to the music quality section. At least I can get it to work properly though.
There was a rumor that Apple Music was the “best” choice for streaming audio because it could be streamed directly to (AAC-supporting) headphones and cars without additional transcoding.
The same theory could apply to Plex and AAC source files.
But I don’t see how that can be true. I don’t think the Phone -> Headphones stream is passed transparently through because other system audio and beeps are mixed in.
I remember listening to my dad’s headphones with their 15 ft. coiled cable. Being admonished not to walk far away or I would break them and be in big trouble.
And him explaining to me why different types of tapes were better and worse for different things. And why it was important to handle records in a specific way. How speakers worked. What Loudness did and “compression” in the audio mastering sense.
Later I could mostly explain to him how a WAV file is a representation of the waveform of a recording, just like a record. And the deep magic of Shannon’s theorem, and why digital audio files aren’t at all like video, with its flipbook of pictures.
And yet here we are in 2020, choosing between codecs so advanced I can’t begin to describe their differences.
And it’s all because cell carriers overcharge for pitiful amounts of data.
for 
s and ■■■■■■ cellular service, transcoding 320kbps MP3 to 128kbps Opus is a godsend 
