Trouble writing tag to mpeg file containing only audio data

[sandersantema]

EDIT: for anyone else seeing this, this was a bug which was fixed in #227

I don't know for certain whether I've run into a bug or if I'm just not using lofty correctly.

I've got mpeg files containing essentially nothing but audio[1] to which I'm trying to write a new Id3V2 tag. For the flac files this works fine in my program:

self.tag.re_map(TagType::VorbisComments);
self.tag.save_to_path(path)?;

I've tried the same for the mpeg files, namely self.tag.re_map(TagType::Id3v2); but that didn't work.
Nor did directly writing to the file handler:

let tag: Id3v2Tag = self.tag.into();
let mut mpeg_file = MpegFile::read_from(&mut file_handler, ParseOptions::default())?;
let _ = mpeg_file.set_id3v2(tag);

I'd like to know the correct way to write the tag. If the above should already work or the correct way doesn't after testing I'll go ahead and open a proper bug report. If needed I can also provide one of the mpeg mp3 files which fails.

[1] Afaik at least, looking at the file with a hex-editor it starts with zeroes until 000001a0:
00ff fbe0 2400 0000 0000 0000 0000 0000
continues with zeroes until 000005b0:
0000 0000 00ff fbe0 0400 0106 cb82 bab3
After which the actual data seems to start.

[Serial-ATA]

Hello!

The first example when using TagType::Id3v2 should work. What errors are you getting?

The second example is only setting the tag for the file in memory, you'll need to either do tag.save_to() or mpeg_file.save_to(), as MpegFile is not tied to any file handle by design.

Afaik at least, looking at the file with a hex-editor it starts with zeroes until

Lofty will skip invalid padding at the start of MPEG files, so that shouldn't be an issue. If the above doesn't work, you can email the file to serial (AT) [domain on my profile] (There's a 25MB attachment limit at the moment).

[Serial-ATA]

Oh no, sorry. I meant if a format is not determined it will search the first 1024 bytes of the file to find the frame sync. That's not implemented anywhere yet, just an idea of how to go about this.

REV_FRAME_SEARCH_BOUNDS is used somewhere completely different.

[sandersantema]

I see, if its not too much asked would you happen to know of a workaround using lofty in the meantime? I prefer a workaround in lofty but luckily already found that ffmpeg repairs the header if the copy method is used: ffmpeg -i input.mp3 -c copy output.mp3, so if there's no good workaround for lofty I'll just use that for a while :)

[Serial-ATA]

Unfortunately, any tag saving will use Probe::guess_file_type() internally, so there's no way to workaround it.

[Serial-ATA]

@sandersantema This was actually simpler to fix than I thought. Could you test out #227 and see if it's able to determine the format now?

[sandersantema]

Done, thank you for fixing this so quickly!