(06-05-2021, 12:03 PM)Nautilus Wrote:

(06-04-2021, 10:54 PM)Tim Curtis Wrote: @Miss Sissy Princess 
The FLAC specification looks quite complete to my eyes.
https://xiph.org/flac/format.html
https://xiph.org/vorbis/doc/v-comment.html

FLAC codec and associated utilities from xiph.org are IME the most widely used in Linux audio precisely because of their high quality implementations, efficient algorithms and well defined specifications.

ALAC is typically only found in collections where iTunes is or was used. Even after Apple released the ALAC specification back in 2011 as Open Source the adoption rate has been almost nil in the Linux audio community because FLAC has been in use since 2001 and was already a proven winner with high quality implementations, speed, efficiency and metadata support.

Oddly Apple still does not support FLAC in the iTunes / Apple Music eco system while most Linux audio players support a wide variety of formats including ALAC.

Just a quick update: I went through my collection and found 1%-2% missing art work, mostly in AIFF files, even if most were fine. After the conversion, I only have a handful of issues out of hundreds of albums, and all for different reasons that I am solving now

(06-04-2021, 10:54 PM)Tim Curtis Wrote: @Miss Sissy Princess 
The FLAC specification looks quite complete to my eyes.
https://xiph.org/flac/format.html
https://xiph.org/vorbis/doc/v-comment.html

FLAC codec and associated utilities from xiph.org are IME the most widely used in Linux audio precisely because of their high quality implementations, efficient algorithms and well defined specifications.

Quote:Field names

Below is a proposed, minimal list of standard field names with a description of intended use. No single or group of field names is mandatory; a comment header may contain one, all or none of the names in this list.

...

• Individual 'vendors' may use non-standard field names within reason. The proper use of comment fields should be clear through context at this point. Abuse will be discouraged.
  
  
• There is no vendor-specific prefix to 'nonstandard' field names. Vendors should make some effort to avoid arbitrarily polluting the common namespace. We will generally collect the more useful tags here to help with standardization.
  
  
• Field names are not required to be unique (occur once) within a comment header. As an example, assume a track was recorded by three well know artists; the following is permissible, and encouraged:
               ARTIST=Dizzy Gillespie
               ARTIST=Sonny Rollins
               ARTIST=Sonny Stitt  
  

https://xiph.org/flac/faq.html Wrote:FLAC has it's own native tagging system which is identical to that of Vorbis. They are called alternately "FLAC tags" and "Vorbis comments". It is the only tagging system required and guaranteed to be supported by FLAC implementations.

Out of convenience, the reference decoder knows how to skip ID3 tags so that they don't interfere with decoding. But you should not expect any tags beside FLAC tags to be supported in applications; some implementations may not even be able to decode a FLAC file with ID3 tags.

Quote:Oddly Apple still does not support FLAC in the iTunes / Apple Music eco system while most Linux audio players support a wide variety of formats including ALAC.

TheOldPresbyope Wrote:How would you suggest the OP "fix" his .m4a files?

(06-05-2021, 11:24 PM)Tim Curtis Wrote: I completely disagree.

Spoon Wrote:That is just it, when there is no official standard the there are sub-standards. Do you know there are 3 ways of storing album artist? it is sad because (although Ogg Vorbis is not going anywhere), FLAC has the potential to become the standard lossless audio codec, but not if there are such blatant incompatibilities. Its main competitors: ALAC and WMA Lossless have no tagging issues.

(06-05-2021, 11:24 PM)Tim Curtis Wrote: You can choose to go Apple ALAC or whatever but 20 years and still going strong the FLAC format has proven itself to be a superior lossless audio format.

(06-06-2021, 10:55 AM)TheOldPresbyope Wrote: Turning this thread into a referendum about FLAC and in particular its representation of audio metadata has done nothing to solve the OP's problem.

The original files are legal MPEG4 containers with audio, metadata, and embedded coverart. However they also contain one or more additional objects which apparently do not conform to Apple's specialization of MPEG4 containers for its M4A format. This in turn apparently confuses the PHP library used in moOde to handle media files. Or something like that.

I now have two solutions to the OP's issue. Either can be executed from the command line in moOde.

1) as I showed before, use ffmpeg to convert the suspect M4A files to FLAC. The AAC LC audio object is transcoded to FLAC, the audio metadata and coverart are transfered in the form specified for FLAC. The additional objects in the container are ignored.

2) as I have since found, one can also use ffmpeg to copy the suspect M4A file to a new M4A file. As before, the additional objects in the source container are ignored.

Example

Code:

pi@moode:~ $ file '01 Dance Yrself Clean.m4a'
01 Dance Yrself Clean.m4a: ISO Media, MP4 v2 [ISO 14496-14]

pi@moode:~ $ ffmpeg -i '01 Dance Yrself Clean.m4a' -c copy 01-fixed.m4a
...

pi@moode:~ $ file 01-fixed.m4a
01-fixed.m4a: ISO Media, Apple iTunes ALAC/AAC-LC (.M4A) Audio

and the resulting track properly plays and displays in moOde just as did the FLAC version I created earlier. Take your pick.

As for the use of metadata in different audio file formats, I find the Picard Tag Mapping Table to be very useful. It is a "list of specific metadata tags defined by MusicBrainz and standard tags, for ID3v2, Vorbis, APEv2, and iTunes MP4."

Regards,
Kent

(06-06-2021, 12:22 PM)Tim Curtis Wrote: Just edit your original post #1. There is a dropdown next to the title.

(06-06-2021, 03:07 AM)Miss Sissy Princess Wrote:

Spoon Wrote:FLAC has the potential to become the standard lossless audio codec...