Gale Andrews wrote:
> | From LRN<
lrn1986@...>
> | Sun, 13 Jul 2008 10:17:01 +0400
> | Subject: [Audacity-devel] Export Options
>
>>>> Gale Andrews wrote:
>>>>
>>>>
>>>>> 8 kbps LC> iTunes: 18 kbps LC
>>>>> 16 kbps Main> iTunes: 19 kbps no profile
>>>>> 32 kbps SSR> null file 0 bytes
>>>>> 32 kbps LTP> iTunes: 22 kbps no profile
>>>>>
>>>>> Should 32 kbps per channel in Audacity end up as 64 kbps given I had
>>>>> a stereo file?
>>>>>
>>>>> DBPowerAmp sees the correct profile for the three files that exported,
>>>>> but has 0 kbps bit rate. Foobar 2000 displays all the exported profiles
>>>>> correctly, and displays the same bit rates as iTunes (i.e. not what
>>>>> Audacity exported).
>>>>>
>>>>>
>>>>>
>>>> Actually, it said "per channel", but in reality it was "per whole file",
>>>> because FFmpeg is making the bitrate/channels division internally.
>>>> Part of the problem is that max supported bitrate is per channel only,
>>>> and it depends on samplerate.
>>>>
>>>> I know how to handle that, but ShuttleGui is resisting my attempts to
>>>> change the data.
>>>>
>>>>
>>> I don't know how finnicky iTunes is, but it's more important that we
>>> get the profile appearing correctly in iTunes than in other programs,
>>> because of the number of people using it.
>>>
>>>
>>
>> Installed iTunes. Impressive. This is the slowest software player i ever
>> encountered.
>>
>
> :=) Plays with no gaps between files though, one thing in its favour.
>
So does foobar2000.
> * MP4 (AAC) bit rates don't seem right for higher bit rates yet. At
> 44100 Hz sample rate I got a 48 kbps stereo MP4 to show as
> 99 kbps in iTunes and Foobar (so near enough?), but stereo
> 96, 193 and 258 kbps files all show in Foobar and iTunes as
> 152 kbps
>
From faac commandline encoder help:
-b <bitrate> Set average bitrate (ABR) to approximately <bitrate>
kbps.
(max. value 152 kbps/stereo with a 16 kHz cutoff, can be raised
with a higher -c setting).
-c <freq> Set the bandwidth in Hz (default: automatic, i.e. adapts
maximum value to input sample rate).
Should i add cutoff frequency to dialog? Or just leave things as they are?
> * Can we have the bit rate list for AAC and MP4 (AAC) ordered
> lowest first as per the other formats?
>
Yes.
> * Were we going to have an M4A filter so that Windows users
> of iTunes don't have to rename AAC to M4A before export,
> and Mac users of iTunes don't have to rename both AAC and
> MP4?
>
Elaborate a bit more, which filters for which platform i should make and
what should they do exactly?
While i had iTunes installed, it played mp4 files without problems.
> * Real Audio is still a problem. Real Player, JetAudio and MPC don't
> understand Audacity's RA files. On my system, only VLC (which
> does not support Real) will play them. As Richard said, RA (like
> it or not) is one of the key formats.
>
Files produced by FFmpeg can't be played either.
> * GSM: Is the WAV version of these as compliant as can be? WMP11,
> MPC and iTunes won't play them and I think they should? Only
> QuickTime plays them on my machine, but there is a slight problem
> even there, a 45 seconds file only lasts 9 seconds in QuickTime.
>
>
Yes, they should.
On the other hand, in Audacity we have libsndfile which is capable of
encoding GSM-WAV. In theory.
> * Both Richard and I would prefer sample rates were taken out of
> of format options for sake of consistency. Do you see any drawbacks
> to this?
>
Well, now for AAC encoding bitrate range depends on sample rate. Either
i have to make the dialog aware of the AudacityProject contents, or
leave as it is.
For other formats removing sample rate is easier.
What should be Audacity's policy when track's sample rate doesn't
matches any of the sample rates supported by format? Error message?
Upsampling? Downsampling? Up/Downsampling (to closest rate)? Forced
resampling (for formats such as GSM which supports only one sample rate).
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