Thanks! Your answer is very helpful !
I want to use malloc() because our algorithm is very complicated. It is
difficult to determine how much memory is needed. I mean the memory needed is
dynamic for different input data. Therefore it is not convenient to allocate
the memory in advance. How do you solve the problem? Requesting a buffer large
enough in algAlloc() ?
----- Original Message -----
From: Ring, Chris
To: Cheng Yang ; davinci-linux-open-source@linux.davincidsp.com
Sent: Friday, March 28, 2008 11:37 AM
Subject: RE: Memory operation in the DSP side
In a closed system, where you only have to interoperate with yourself, you
can do whatever you want. I don't think there's any limitation in Codec Engine
or BIOS that will prevent you from calling malloc/free from within your
algorithm.
Your algorithm would obviously fail any xDAIS validation testing. ( And on
that note, here's a quick pitch for the resurrected QualiTI tool available in
xDAIS 6.10, and the new TI eXpress DSP wiki here:
http://tiexpressdsp.com/wiki/index.php?title=QualiTI_XDAIS_Compliance_Tool )
As your signature indicates you're from a University, this may be an
opportunity to share the reasons xDAIS places this restriction on algorithms
with your students, and help them understand why calling malloc/free are not
"good things to do" in an open environment. Here are a few:
* malloc() and free() are often non-deterministic, so methods calling
malloc()/free() lose their determinism
* malloc() can fail(!), what should your algorithm do if that happens?
xDAIS algs restrict failures due to lack of resources to creation time.
* malloc() and free() don't provide fine-grained _types_ of memory
requests (e.g. internal, external, scratch, persistent, etc) which complex
algorithms typically need.
* and as a result, the use of malloc()/free() hinders frameworks (like
Codec Engine and Framework Components) from sharing scratch resources across
algorithms, which complex systems with many algorithms typically need.
Chris
----------------------------------------------------------------------------
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Cheng Yang
Sent: Thursday, March 27, 2008 8:16 PM
To: davinci-linux-open-source@linux.davincidsp.com
Subject: Memory operation in the DSP side
Hi, all
I am developping an algorithm for the DSP. In the Codec Engine framework,
the codec is run in the DSP/BIOS. And the codec has to be complied with the
xDAIS standard. So the codec is not allowed to do any memory alloction
operation. It is for the convenience of algorithm users. However, in our
project, we are not going to export the codec to others, which means we
will provide the DSP server directly. So will it be safe for the codec to
do memory operation such as malloc() and free()?
Any discussion will be appreciated!
Best regards!
---------------------
Cheng Yang 杨成
Digital Signal Processing and Transmission Lab
E.E. Department, Fudan University
Shanghai, P.R. China
Lab: +86 (0) 21 65643633
Mobile: +86 13818155051
Email: [EMAIL PROTECTED]_______________________________________________
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