Re: [mpeg2-dev] RAM and binary size

[Patric L. <pl...@it...>]

I don't know all the details, but a few things though:

The example source code (mpeg2dec) uses a stream
buffer of 256 KB (kilo bytes). This is MPEG2 DVD
streams video buffer requirements (AFAIK). But you
can use smaller sizes if you want.

The decoder engine requests the output driver to
allocate three frames for YUV backing storage, three
frames are required for inter-frame coding.
I think most drivers allocate 720*576 + 2*360*288 =
622080, three frames thus require 1.8 MB.

According to top, while running DVD MPEG2-decoding,
SIZE is 2900, as well as RSS, SHARED is 2500. From this
I would say it requires about 3 MB (text+data+stack)
and additional 2.5 MB of shared text+data (shared objects).

Playing MPEG2 on hand-helds it feels reasonably to use
much lower resolution (recoding on a server). I think
you might need to patch the code to have it allocate
just the amount of frame buffer sizes needed.

About computing power: My 1 GHz laptop decode
just above 100 frames-per-sec using MMXEXT for
IDCT and motion compensation. With linear scaling,
you would need 333 MHz for just decoding NTSC, if you
have MMX instructions, that is, you can do
4 int ops/instruction.

I see a Compaq iPaq have a 206MHz Intel StrongARM.
So I guess full 720x576 video decoding is out of
the question. Suppose you have 240x192 video
(fits on iPaq), this is 1/9 of original size,
if this scales well with processing requirement,
you would need 37 MHz for 30 FPS video (if
all instructions take the same amount of
clockcycles). Without MMX, you need 148 MHz.

So, hard to tell, it might possible. I don't
know enough about Hand-helds CPUs.

/ Patric

Ian Ethan wrote:

> Hi,
> I am trying to run the libmpeg2 library on a small
> hand-held. I have been trying to get some data out of
> an ordinary desktop Linux machine concerning  the RAM
> consumption and executable size, but I am quite new to
> the Linux world, and I haven't managed. Could you
> please tell me what is the actual binary size of the
> library - excluding external required libraries such
> as SDL, but including the actual decoding engines.
> and also what RAM consumption I should expect. If you
> could give me those numbers for the latest version of
> the player I would greatly appreciate it.
> Thanks.
> Ian.
> PS:any data you might have concerning the processing
> power needed might be also helpful. Do you know for
> instance if there is a way of trimming the player to
> make it work on a small hand-held?
> By the way how big is the mpeg2dec package?