"Sample Rate" -- extremely important, please read

Gesine · Post by **Gesine** » February 18th, 2006, 4:14 am

We should perhaps mention where readers can find their sample rate settings. Usually this is in the preferences. In Audacity, the sample rate is displayed at the bottom of the recording window - it says: "Project rate: 44100". If it's more than 44100, it can be changed in Preferences > Quality, under Default Sample Rate.

Peter Why · Post by **Peter Why** » February 18th, 2006, 4:53 am

You can also change it in Audacity from the ?control box that opens at the left end of every recording. Click on the title bar of the box and you get a pull-down menu. Sample rate is at the bottom.

Peter Why · Post by **Peter Why** » February 20th, 2006, 7:28 am

So, I have a block of twenty mp3 poems (collection 004) ready to upload. The only sound software I have (as far as I know) is Windows Media Player and Audacity. Is there any easy way to determine the sample rate of these files? I would prefer not to do it by importing into Audacity, as the program takes some time to convert the mp3s.

Gesine · Post by **Gesine** » February 20th, 2006, 7:36 am

Don't know about Windows Media Player. You could download iTunes (which is free) - it imports mp3s within seconds. Right-click on the track and click 'Get info' - the sample rate is displayed there.

If someone can find an easy way to convert sample rates on a Mac (again, don't want to use Audacity), I'd be grateful.

vee · Post by **vee** » February 20th, 2006, 7:38 am

Peter, if you're using Windows XP you should be able to right click on the MP3 and choose "Properties" Then choose the Summary tab. You might have to toggle to the advanced view, but towards the bottom of the Summary should be the sample rate, Duration, Bit Rate, Sample Rate, Channels

Peter Why · Post by **Peter Why** » February 20th, 2006, 7:43 am

Thanks; I'll try for the Properties through XP.

Gesine · Post by **Gesine** » February 20th, 2006, 2:46 pm

I've just been asked how to set the sample rate in GarageBand. Answer: there's no need. GarageBand always records at 44,100, the rate we need.

Linton · Post by **Linton** » February 21st, 2006, 8:17 am

Hello everyone,

I have been sent to this thread by 'the management'

to humbly beg the community to continue accepting my 32khz files without resampling them

I find 32khz to be the optimal sample rate for voice recordings, both from the point of view of my own equipment, and as a general recommendation considering how they are going to be used here (bit rates, recompression process etc). I will refrain from giving a passionate technical defence of this view until asked

Just to add my 2 [currency units of your choice] worth on the compatibility debate more generally, almost any well-behaved software or hardware player should be fine at 16, 22.05, 24, 32 or 44.1khz.

The lower sample rates (8, 11.025 and 12) are only supported in MPEG 2.5 (layer 3), an unofficial version (from a standards point of view) created by the MP3 patent-holders. This is quite widely supported now, but is designed mostly for low bit rates. The are several buggy players, including WinAmp, that will misbehave when fed a 128kbps MP3 file at these rates.

48khz is part of the original MP3 standard, so devices have no excuse not to support it, but since I do own one such sulky player (a RioVolt), I am aware that it can be a problem and wouldn't advocate its use here.

Does anyone else know of any other widely-used misbehaving players we may need to make allowances for?

ChipDoc · Post by **ChipDoc** » February 21st, 2006, 8:31 am

Linton wrote:48khz is part of the original MP3 standard, so devices have no excuse not to support it, but since I do own one such sulky player (a RioVolt), I am aware that it can be a problem and wouldn't advocate its use here.

Well first off, welcome to LibriVox, Linton - It's great to have a fresh voice in the mix!

I don't believe that the issue was with the MP3 players. The real problem was with the validator software which allows us to upload these files to Archive.com - they choke on a lot of these rates.

You can continue to send at 32000 if you need to; it won't prevent them from being used here on LibriVox and we're happy to get them. It's much more difficult to find good readers than to find the time to upconvert an odd file or two to the 44100 standard so the validator will allow the file to pass.

HerrSchildkroete · February 21st, 2006, 9:22 am

Hi Linton,

Linton wrote:Hello everyone,
I have been sent to this thread by 'the management' to humbly beg the community to continue accepting my 32khz files without resampling them

I find 32khz to be the optimal sample rate for voice recordings, both from the point of view of my own equipment, and as a general recommendation considering how they are going to be used here (bit rates, recompression process etc). I will refrain from giving a passionate technical defence of this view until asked

You are certainly right in claiming that 44100 is a little overdone for voice - however I think all the files should be the same sample rate. I tend to merge files before putting them on my player (an iPod). However the iPod does not cope well with sample rate changes inside the file.
And the main point in favor of 44100 is, in my opinion, that most recording software nowadays uses that as a default

Linton · Post by **Linton** » February 21st, 2006, 9:57 am

Hello Chip, and thanks for the welcome.

Could you please explain this mysterious 'validator' software to me?

Initially I assumed that the 'forbidden files' were those that confused archive.org's re-encoding system, so I was relieved when my first files were uploaded (and derivatives generated) sucessfully.

Then, reading this thread, much of the discussion seemed to be about player problems, a test I think 32khz files should generally also pass.

So why does 'mister validator' object?

It's a question of quality rather than convenience - I would rather resample myself from the originals than end up with a further loss in quality from someone else doing it from the MP3 and having to re-encode. However, even if I resample myself, if a 44.1khz file is used it will result in lower sound quality for the listeners than if 32khz was permitted. This is because higher sample rates carry an overhead 'cost' even in lossy encoders such as MP3, but the extra frequencies provided contain no signal, only noise or nothing, for most voice work, certainly in the case of my equipment.

I am reluctant to start producing lower quality files without a good reason, so I'm looking for 'a good reason' or permission to use 32khz and have them left alone, basically.

HerrSchildkroete: You're correct that merging files with different sample rates is asking for trouble, but why do you need to?

raouf · Post by **raouf** » February 21st, 2006, 10:03 am

Peter Why wrote:Is there any easy way to determine the sample rate of these files? I would prefer not to do it by importing into Audacity, as the program takes some time to convert the mp3s.

Don't know about Windows Media Player but Winamp is a freely-downloadable media palyer which clearly displays the sampling rate of the file played.

HerrSchildkroete · February 21st, 2006, 10:08 am

Linton wrote:HerrSchildkroete: You're correct that merging files with different sample rates is asking for trouble, but why do you need to?

That's because of my listening habits. I usually listen to the recordings while travelling. On a train, on a bus, while walking. So I merge the files and recompress them to aac. That way I can take advantage of the bookmark feature in the iPod and additionally have a single file for a single book.
I prefer that over the sound quality

.

kayray · Post by **kayray** » February 21st, 2006, 10:19 am

HerrSchildkroete wrote:
Linton wrote:HerrSchildkroete: You're correct that merging files with different sample rates is asking for trouble, but why do you need to?
That's because of my listening habits. I usually listen to the recordings while travelling. On a train, on a bus, while walking. So I merge the files and recompress them to aac. That way I can take advantage of the bookmark feature in the iPod and additionally have a single file for a single book.
I prefer that over the sound quality :-).

Oh wow... that's brilliant!!!

LibraryLady · Post by **LibraryLady** » February 21st, 2006, 11:22 am

I'm confused, I thought the problem was with mp3 players, not the validator?? Everything was fine and the validator gave us no trouble, I thought this all came up become someone couldn't play something on their mp3 player. Maybe I'm thinking of something else?

Linton - the validator is a nifty tool that we MCs use in the cataloging process. Chris (tis) created it for us and it helps us review the files before the big upload to archive and also enter information about the project which it then uses to generate HTML for the catalog page. Basically it saves us a lot of time and catches potential problems before the big upload.

So, are we officially allowing other sample rates again?? If so, we need to be specific about which ones are okay and update the wiki and posts so we are consistent.