Re: Crash Proof Apple Lossless
Re: Crash Proof Apple Lossless
- Subject: Re: Crash Proof Apple Lossless
- From: Dominic Feira <email@hidden>
- Date: Sun, 16 Nov 2008 13:05:56 -0500
You are missing the point. I'm talking about the file format, not the
API. Computers crash, it's a fact of life. People want to be able to
salvage any recordings that were in progress. It's not necessarily
even my app that is crashing. Kernel panics happen. The idea is that
the file format should be resilient so the recording isn't lost. In
my testing the following file formats meet this requirement:
AIFF, WAVE, SDII, mp3, AAC ADTS, AMR, and CAF with a format that
doesn't require a packet table. My goal is to be able to use Apple
Lossless in a crash proof setup.
I know that I can write my own audio file format that will accomplish
this, I was just hoping not to. For what its worth, it might be
possible to salvage the audio data in a "crashed" CAF with Apple
Lossless. I am going to be exploring this avenue first.
-- Dominic Feira
On Nov 16, 2008, at 5:01 AM, tahome izwah wrote:
If you get crashes you're probably accessing an instance of an EAF
(ExtAudioFile) object from different threads. The EAF API is not crash
proof when used from different threads. Either create your own EAF
instance in each thread or use plain AudioFile calls.
If that's not the reason I would file a bug report with Apple
http://bugreporter.apple.com
--th
2008/11/16 Brian Willoughby <email@hidden>:
I believe that CAF was designed to be crash-proof. Check the
specification,
available from Apple, or perhaps someone else here can confirm. I
believe
that only SDII and CAF are crash-proof. However, if you're using
CAF to
hold Apple Lossless encoding, then I'm not sure whether the crash-
proof
feature would be fully possible. On that note, I'm not sure that any
compressed coding will preserve as much audio data during a crash
as an
uncompressed coding. You may have to choose between the space-
savings of
compression and the reliability of a fully crash-proof format.
Brian Willoughby
Sound Consulting
On Nov 15, 2008, at 16:53, Dominic Feira wrote:
On Nov 15, 2008, at 3:03 PM, tahome izwah
2008/11/14 Dominic Feira <email@hidden>:
Hi. I rely quite heavily on Apple Lossless audio. I would like
to crash
proof recording to Apple Lossless. MPEG-4, CAF, and QuickTime
Movie all
require that the file is closed properly in order to open them.
Just curious: Where did you get that info from?
We're accessing files that are open for writing from a separate
ExtAudioFile instance (for reading) without problems in one of our
apps. You might need to call AudioFileOptimize() to flush data to
the
file before you can read them but other than that we've not had any
problems with it...
--th
My concern is recovering from a crash. In all of the mentioned
formats if
the app crashes before the file is closed the packet table is never
written
to the file. It isn't possible to flush data to the file if the
app has
crashed.
-- Dominic Feira
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Coreaudio-api mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Coreaudio-api mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden