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FS#6942 - Bug with bitrate determination

Attached to Project: Rockbox
Opened by Roma (Didro) - Friday, 30 March 2007, 13:29 GMT+2
Task Type Bugs
Category Music playback
Status Closed
Assigned To No-one
Player Type iPod Nano
Severity Low
Priority Normal
Reported Version
Due in Version Undecided
Due Date Undecided
Percent Complete 100%
Private No

Details

I have MP3 file which is 2 hour long and has bps = 192, but rockbox player determinates that bps = 24 (which is 192/8) and lenght = 16 hour (2*8). Apple's firmware and Winamp show information about this file correctly.
This task depends upon

Closed by  Jens Arnold (amiconn)
Tuesday, 17 April 2007, 20:04 GMT+2
Reason for closing:  Not a Bug
Additional comments about closing:  Rockbox relies on the Xing VBR header if the file is VBR. If it isn\'t present it assumes CBR and does its playtime calculation based on the bitrate of the first frame. PC based media players can check the whole file to determine the correct bitrate, rockbox doesn\'t do this in order to save battery. Adding a proper Xing header to the file will fix the display in rockbox. One option is to use the vbrfix plugin, as you did.
Comment by Linus Nielsen Feltzing (linusnielsen) - Friday, 30 March 2007, 13:34 GMT+2
I would like to have the file for analysis, else I can't find out what is wrong.
Comment by Roma (Didro) - Friday, 30 March 2007, 14:05 GMT+2
>>> I would like to have the file for analysis, else I can't find out what is wrong.
It has 180 MB, so its unreal to upload it for me. It is interesting for me where does rockbox player take information about length of file?
Comment by Linus Nielsen Feltzing (linusnielsen) - Friday, 30 March 2007, 14:25 GMT+2
The bitrate and the length is taken from the MP3 frame headers, and/or the Xing/LAME header. In fact, it is only important to have te first megabyte of the file, if you are able to cut it out for me. Don't cut it with an audio editor, but with a hex editor or similar, for example the 'dd' tool.
Comment by Roma (Didro) - Friday, 30 March 2007, 15:02 GMT+2
OK, I'll try. I think maybe in MP3 header of this file is invalid information, but Apple's firmware and different windows programms can determine bps and length in some other way. I'll also test this file by different Mp3 readers.
Comment by Roma (Didro) - Friday, 30 March 2007, 16:46 GMT+2
I've open this mp3 with VBRfix, now it shows me lenght: 1 min 10 sec, bps: 19646 :-)))

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