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Subject: Re: Looking for converter "MPEG 2.5" -> "MPEG 2"

Re: Looking for converter "MPEG 2.5" -> "MPEG 2"

From: Jens Arnold <arnold-j_at_t-online.de>
Date: 2006-06-14

On 13.06.2006, A. Lester Buck III wrote:

> ...
> I have one small issue with my Archos, and I was hoping
> someone could point the way. Some of the MP3s I want to play
> are delivered in the format listed as "MPEG 2.5 Layer III" at
> 24kBit/s and 11025 Hz. This format is apparently not supported
> on this older unit.

Are you sure that the files that don't play are really MPEG2.5
layer 3 at 24kbit/s, 11025Hz? While the hardware decoder used in
the archos Player/Studio does have some limitations for MPEG2.5
and doesn't play the full range of bitrates, 24kbit/s at 11025Hz
should work. The page
http://www.rockbox.org/twiki/bin/view/Main/MasLimitations
shows my findings about the limitations of the MAS codecs.

However, if the files are really 11025Hz 24kbit/s and don't
play, then the only reason I can imagine is that there must be
several revisions of the MAS3507 with differing capabilities
regarding MPEG2.5. Would be interesting to find out...

> Files in the format "MPEG 2 Layer III" at 24kBit/s and 16000
> Hz play fine. (Oddly, the 2.5 format apparently doesn't even
> save space.)

While 24kbit/s at 11025Hz don't save space compared to 24kbit/s
at 16000Hz, the former means less compression and hence higher
quality than the latter. This is the nature of lossy compression
- it's a tradeoff between quality and file size. Higher sample
rate means more data to compress.

Regards, Jens
Received on Wed Jun 14 07:52:17 2006


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