Distorted audio on phone - only on tracks edited in Audacity

New to Audacity. Using it to digitise my vinyl LPs. LPs mostly in as new condition, so I export to flac format to enable metadata entry and lossless format, and almost always with no editing of the audio in Audacity, as I just want my LPs accessible wherever, with minimum effort. All good, everything plays back with good quality on all devices I tested, until I tried some editing.

On a couple of LPs with scratch damage on the first minute or 2 of the lead-in tracks, I first tried Click Removal, but the entire track then had very distorted audio, and on every playback device.
Then tried zooming in and using Repair on just the click waveforms. That also appeared to work well, until I tried listening on my phone with earbuds.
As an example, I digitised a 2-LP set with 9 pieces of classical music, then repaired the clicks as above on only 2 of the pieces. Used Export Multiple to create 9 flac files. The 7 pieces I haven’t edited play as expected. The 2 files I have edited have severe distortion throughout, but only when played on my phone.

The files are stored on a Synology NAS. At home I play back via the media player function of a home cinema system and the 2 edited files play without distortion. I can play the same 2 files on an Android tablet via wi-fi 6 with various different media player apps, all ok.

If I play the same 2 files on my phone with the same media player apps as the tablet, and connected via wi-fi 6, there’s severe distortion. The 7 unedited files play just fine on the phone. So the only differentiating factor is the minor click repairs of the 2 files in Audacity.

Any ideas?

The differentiating factor could be the bit-depth of the FLAC file you made in Audacity
not all FLACs created equal
Some devices will produce extremely distorted playback if the bit-depth is greater than 16.

Note that the “level” doesn’t affect quality. At higher levels it takes more time compressing to make a smaller file. But FLAC is always lossless compression (unless you reduce the bit depth).

Thanks! I just learned something!

Thanks for the quick reply. The bit-depth is 24, but that would apply also to the 7 files that haven’t been edited and play without distortion. I can try re-exporting at 16 bit,
Just after posting earlier, I thought of another test and that throws some light on the subject.
I downloaded the 2 files with distortion onto the internal storage of my phone, from where they now play without distortion.
The Synology NAS can do some automatic media file conversion on the fly, depending on the target device playback capability and the connection speed. So it seems likely that somehow the Audacity editing process on the 2 modified files is tricking the NAS into doing something strange with the audio stream, but not on the unedited files.
I’ll have to dig into the NAS settings. Maybe it’s a question for the Synology forum.

How about the edited files actually being much louder than the other 7,
but some (not all) of your media players are automatically turning their volume down :thinking:

How is the NAS connected to your editing machine? Network?

Audacity doesn’t much like editing on non-internal drives.

Koz

The project is edited and saved on an internal SSD in my HP ZBook workstation. Export multiple is used to create the flac files on the same internal SSD, so all the flac files, the 7 with no distortion and the 2 edited ones, are all created with the same settings and saved as separate files via the names on the label track. Then the finished flac files are copied to the SSD in the NAS.
Having done more testing, the 2 edited files play normally when streamed from the NAS via ethernet to the media player in a Blu-Ray player, or a TV, both connected via HDMI to a home cinema system. Also no distortion when streamed via wi-fi from NAS to ZBook.
When streamed to my phone, either via wi-fi AX or 5G mobile data, the 7 unedited files play without distortion, and the 2 edited files have severe distortion. If the 2 edited files are downloaded to the phone storage they then play without distortion.
So by a process of elimination I have determined that the NAS media player treats the 2 files edited in Audacity differently from the 7 unedited ones, and only when streaming to my phone.
I need to test the effect of selectively turning off the downsampling options in the NAS media server. These can be enabled or disabled for each audio file format, and are applied automatically depending on the receiving device. But it’s weird that the distortion occurs only on files edited in Audacity, and not on similar files where no editing was done. The distortion is constant and not volume dependent on soft or loud passages in the music.

Did you compare the “good” and “bad” files with MediaInfo?

…It’s hard to imagine NAS changing the format. It should just be storing files. And if you were getting file corruption you’d probably be seeing it with other files.

If it’s not just storage and it has a built-in streaming server application, it could be re-compressing audio/video files.

Audacity does want a local NTFS drive for AUP3 projects, and I think for recording also. But you can move AUP3 files around freely outside of Audacity, as long as you copy it back to local drive before re-opening it.

The Audacity-edited tracks may lack ReplayGain-type metadata, which tells the player to turn the volume down. [ Audacity has been known to discard metadata fields ]

Mediainfo does show all the metadata present on the file.

Thanks for the MediaInfo tip, which I’ve now installed. There are no differences in the metadata that look significant in the edited vs. non-edited files, but I need to re-check that using the same audio file, before and after editing.
The NAS does have DLNA media server apps for video, audio and photos, these can downsample on the fly depending on the playback device. So I think I’ve narrowed down the problem to some interaction between that and the decoding on the phone’s audio player, but only when the FLAC file has been edited in Audacity, as opposed to simply exporting the recorded audio.
There are also Synology media player phone apps, but the distortion is there in those, MX Player, and the phone’s own player.
I need to do a like for like test with one small audio file 1) Record from LP, 2) Export as FLAC without editing, 3) Edit some clicks out then export same file as FLAC. 4) Compare the results by listening and by looking at the metadata. 5) If the problem is reproduced, then experiment with different FLAC compression levels to see if that makes a difference, as higher compression might need more decoding resources.
6) I Checked the phone specs (Galaxy S20+ 5G) to confirm if it can play FLAC files. That might tell me if the compressed audio would be decoded by the NAS or the phone.