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Topic: Fix MP3 Header (Read 9793 times) previous topic - next topic
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Fix MP3 Header

How do I use the Fix MP3 Header function in v0.8.3 to specify the exact amount of silence my file has? Is it impossible by design of the Xing-Lame frame? When I type in the length in samples I want, after reopening I found the value automatically adjusted (rounded?) and gapless playback ruined.

Length of file: 12,003,311
Silence at start: not important
Silence at end: 240

I set the delay = 576, length = 12,003,311 - 576 - 240 = 12,002,495

For some reason the thing gets rounded down to 12,001,583

Fix MP3 Header

Reply #1 –
Oh, never mind. The problem is not present in v0.9.4.1 which I tried on NT at work.

Fix MP3 Header

Reply #2 –
Where did you find that function on 0.9x? I've been looking forever.

Fix MP3 Header

Reply #3 –
You might have to add the option (and any other MP3 utility commands which you desire) to foobar2000's context menu via the preferences. After that, it should be within the Utils submenu.

Fix MP3 Header

Reply #4 –
There is a problem in v0.8.3... it doesn't always recognize the delay and padding values. I've corrected an album in v0.9.4, but only half of the corrections appeared in old Foobar. It did detect the "Info" frame, said mp3_accurate_lenth = yes, but no numeric values. Can you tell me what the bug was?
 

Fix MP3 Header

Reply #5 –
After a discussion with Omion I've discovered that Foobar 0.9 does not create the complete Xing frame for CBR files, i.e. it does not generare the TOC. This might be the reason, why Foobar 0.8 refuses to detect the header.

Omion also claims that Foobar does not calculate the CRC checksum of the Xing-LAME frame (I did not know there was a CRC until now), making the added frame invalid and therefore other software should not look for LAME-specific data there (delay, padding, encoder configuration).

Fix MP3 Header

Reply #6 –
Quote from: j7n on
...Foobar 0.9 does not create the complete Xing frame for CBR files...
...Foobar does not calculate the CRC checksum of the Xing-LAME frame...

Time for a Fb2k v0.9.5 release ?

Fix MP3 Header

Reply #7 –
(bump)
Thanks in advance for any, official or even "backstage", information about this MP3 uncompilancy...

Fix MP3 Header

Reply #8 –
Quote from: j7n on
After a discussion with Omion I've discovered that Foobar 0.9 does not create the complete Xing frame for CBR files, i.e. it does not generare the TOC. This might be the reason, why Foobar 0.8 refuses to detect the header.

Omion also claims that Foobar does not calculate the CRC checksum of the Xing-LAME frame (I did not know there was a CRC until now), making the added frame invalid and therefore other software should not look for LAME-specific data there (delay, padding, encoder configuration).


I actually don't think the TOC is required for LAME tags. I know it's optional for an XING tag and the LAME tag spec just gives a zone for the "Traditional Xing VBR Tag data", which I assume follows the same rules... it's not clear, though.

The CRC issue, however, is definitely a problem. Without the LAME CRC data, that frame is not a valid LAME tag. Only with the CRC intact can you be sure (well, 99.9985% sure) that the frame contains valid LAME information.

The issue came up when I noticed that my mp3packer program wouldn't accept the padding data from 0.8.3's "Fix MP3 Header". I realized that Foobar was only updating the 3 bytes that stored the header, and not changing the CRC to reflect that. I made a workaround in mp3packer to accept incorrect CRC data if the padding is the only nonzero data in the frame. However, now it looks like Foobar 0.9 also fills in other parts of the LAME tag, but still doesn't update the CRC...
"We demand rigidly defined areas of doubt and uncertainty!" - Vroomfondel, H2G2

Fix MP3 Header

Reply #9 –
bump again (sorry, but it's a quite serious bug...)