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[Alex B]

leezer3 posted this:

Media Center 13.0.165
« Reply #7 on: Today at 06:58:00 am »   

Just had a rather frustrating few minutes, and caused a wholly repeatable send/ don't send crash into the bargain 
Background-
I've acquired a file in mp2 format (Can post it if necessary). MC plays this file fine, but typically my N95 doesn't, so my first step was to try and get MC to convert it- This is where I caused the crash. Steps to reproduce:
1. Add a non-supported audio file format to the conversion queue. MP2 was what caused it here.
2. Click the convert button. As expected, the can't convert dialog box pops up. However immediately after this, MC crashes.

Couple of things I note- Currently, MP2 is down as a video format. While it may be more widely used as such, afaik this is a misuse of it (mp2 is defined as audio in ISO/IEC 13818-3); Should it be added to both, especially as MC recognised the mp2 file correctly as audio in the first place
Also, it's also a tad frustrating that the mp2 file converted nicely when renamed to mp3- Could the conversion process please take this into account?

MC's internal decoder is fully capable of decoding MP2 (aka MPEG-1 layer II) audio files and also analyzing and tagging them (ID3v1 & ID3v2). MP2 files work fine when the extension is changed to MP3. The tagged files are compatible with many other programs when the extension is changed back to MP2.

A request: Please add internal support for the MP2 audio format. You don't need to change anything else than set MP2 files to use the internal MP3 decoder by default.

I don't know any other program that considers MP2 as video. MC has support for several other filename extensions that are commonly used with MPEG2 video files.

http://en.wikipedia.org/wiki/MPEG-1_Audio_Layer_II

EDIT

Here's a sample file: Never_Forget_You.mp2.zip (1.4 MB). I encoded it with Wavelab 5. It's bitrate is 384 kbps. It has standard ID3v1.1 and v2.3 tags.

[Matt]

I have some .mp2 video files as well.  They're old so I don't know where they came from.

I suppose we could special-case mp2 to try to pick the correct engine for it?

[leezer3]

It would be nice
I'm presuming most of the code is already in place, as MC recognised the mp2 as audio rather than video.

Having said that, I've only run into one mp2 file in the time I've been playing with media, so it's not really a priority but an inconvenience for one file. (Now converted to pure mp3 anyway)

Cheers

-Leezer-

[Alex B]

I fixed the sample link. It wasn't correct. Please try the sample as it is and after that change the extension to mp3 and try it again. When the extension is mp3 you can read and write tags and use replay gain.

I have some .mp2 video files as well.  They're old so I don't know where they came from.

I think your case is mentioned in the wiki article: "The abbreviation MP2 is also sometimes erroneously applied to MPEG-2 video."

MC already has the following other extensions for MPEG2 video: mpg, mpeg, mpv, mpe, and m2v. MP2 could well be dedicaded to MPEG-1 layer II audio files.

In general MPEG-1 layer II is an old lossy format that produces mediocre quality when compared with the modern lossy formats (AC3 is equally old and not any better in this sense). Unfortunately MPEG-1 layer II is the standard audio format in DVB-T and DVB-C radio and television broadcasts. At least here in Finland all brodcasters use MPEG-1 layer 2 stereo audio stream @ 224 kbps. That includes the DVB radio channels. If I want to record DVB radio (or video and demux the audio stream) in the original digital format I'll have MP2 audio. It's audio quality is already compromised and transcoding to some other lossy format would be a bad idea.

[Alex B]

BTW, I don't think the opinions about MP2 quality in the linked Wiki article are necessarily true. The article claims that MP2 is as good as MP3 at higher bitrates, from 192 kbps to 384 kbps. I ABX tested some problem samples that were encoded in MP2 format at 192, 256 and 320 kbps. I think they were easier to distinguish from the lossless source than LAME MP3 VBR at about 200 kbps. The writer(s) may not be aware about the constant development of the LAME and some other MP3 encoders. As far as I know, the MP2 encoders have not practically changed since the 90's and in general the format limits what is possible. For instance, Musepack was originally based on MPEG-1 layer II, but it was radically changed before it became what it is now.

The other, technical, descriptions in the article seem to be quite correct.

[Alex B]

The sample link in the first post has expired.

Here is another ID3 tagged MP2 sample file in a zip package: http://rapidshare.com/files/326633216/Discipline.zip (12.1 MB)

(It is a re-encoded track from NIN's free The Slip album. The album is freely available at http://theslip.nin.com/ .)


EDIT

If rapidshare is congested here is an alternative link: http://www.megaupload.com/?d=QC1K539T

EDIT 2

Both services seem to be quite busy at the moment...

EDIT 3

The hosting services do not work. I attached a short sample clip. (Log in to the forum if you can't see the attachment.)

EDIT 4

The reason to provide a new sample link now is this thread: http://yabb.jriver.com/interact/index.php?topic=55377