Posted by fred-bloggs on 11/17/39 11:43

Charles Russell <SPAMworFREEwor@bellsouth.net> wrote in
news:VSdWf.2806$V7.1363@bignews3.bellsouth.net:

> fred-bloggs wrote:
>
>>>
>>>What formats does the Zen player support? I had no luck trying to
>>>find on the web detailed specifications of supported file formats for
>>>the different players, even for Apple. The Ipod my kids gave me for
>>>Christmas handles 16 kHz and even 11.025 kHz, as does the Goldwave
>>>audio editor. If I had been spending my own money and gotten a
>>>cheaper MP3 player, would I be unable to play my highly compressed
>>>low-fidelity voice files directly without reformatting to bigger
>>>files?
>>>
>>
>> Changing the sample rate doesn't alter the size of the mp3 files.
>
> My assumption - am I wrong? - is that a low sample rate effectively
> filters out the high frequencies so that there is less data to
> compress, allowing use of a lower kBps without making voice
> incomprehensible.

You are correct, lower _sample_rate_ at the same _bit_rate_ improves
fidelity.

> My understanding is that 11025 Hz corresponds to AM
> radio, 8000 Hz to telephone. I find that at 11025 Hz, voice is clearly
> understandable at 16 kBps, though with noticable distortion. At 24
> kBps my old ears can't even hear any distortion.

There is very little voice content above 1 khz, so any of those sample
rates should be capable (the sample rate must be at least twice the
highest frequency). You might want to try 8 khz at 16 kbps, just for your
own interest (but see below).

>>
>> Does your Ipod support mp3 @ 8 khz? The Zen does.
>
> The iTunes that came with the Ipod includes 8 kHz this as a menu
> option, but I haven't tried transferring 8kHz files to the player.
> 11025 Hz files work OK. I was afraid that iTunes would automatically
> convert my highly compressed files when transferring to the Ipod,
> reducing the effective storage capacity, but the file size seems to be
> unchanged on the Ipod.
>
> The MP3-CD player in my car supports 16 kHz but no lower (not 11.025
> or 8), so I'm currently using that as my default, hoping that to be a
> portable format for highly compressed recorded lectures. Evidently it
> is portable to both my car player and to the Zen.


OK, Itunes/Ipod probably have 12 khz as well. The sample rates 8, 11.025
and 12 khz are non-standard and are implemented differently by various
coders, as we have discovered :). So yes, stick to a minimum sample rate
of 16 khz if you want compatability with MPEG2.

If you want *maximum* compatability with MPEG1 you should use a sample
rate of 32 kHz and a bitrate of 32 kbps.


--
fred

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