DM3725 Video Encoding issue

jason xu

Prodigy 90 points

Hi,

I am trying to encode the video as examples of DMAI application. It works but the performance is not good.

By printing the time stamp, I found the memcpy costs too much time (~40ms):

Int8 *ptr = Buffer_getUserPtr(hBuf);

memcpy(ptr, g_video_frame_data, 640 * 480 * 2); // this action costs ~40ms

...

Is it possible to reduce this time? I want to record with 30fps, so I hope it can be decreased to <10ms.

Thanks.

Jason Xu

over 12 years ago

0 Cvetolin Shulev-XID over 12 years ago

TI__Guru 65405 points

Hi Jason,

Could you give some details about your board and about RAM clock frequency because 40 ms seems very long time for this memcpy? Also what is your software environment?

BTW if the time for encoding a frame is up to 33 ms it is enough for 30 fps.

Tsvetolin Shulev

0 jason xu over 12 years ago in reply to Cvetolin Shulev-XID

Prodigy 90 points

HI Shulev,

Our RAM has 166M clock. I ever tried to copy the same size data in RAM (from one buffer to another one), it costs only <1ms, so I don't know why it it needs so long time to do memcpy to encoder memory.

Thank you very much.

Jason Xu

0 jason xu over 12 years ago in reply to jason xu

Prodigy 90 points

Because the encoding process (Venc1_process()) costs about 23ms for mpeg4enc, so I hope the memcpy takes <10ms. Thanks.

0 jason xu over 12 years ago in reply to Cvetolin Shulev-XID

Prodigy 90 points

More information:

1) use "malloc()" instead of "Memory_alloc()", this time (memcpy) could be reduced to 3.x ms, but the video encoding doesn't work;

2) enable cache, this time can be reduce to ~30ms, but the writeback will cost some time

0 Cvetolin Shulev-XID over 12 years ago in reply to jason xu

TI__Guru 65405 points

Hi Jason,

There are some differences between "malloc()" and "Memory_alloc()" functions.

Memory_alloc allows you to write your C code once, and then choose a different memory manager in your config script without changing your C code. If you want to use C's malloc, you can select xdc.runtime.HeapStd as your app's memory manager.

Alignments is given in MADUs (minimum addressable data units), which means bytes in most cases. Here is the doc for Memory_alloc:

http://rtsc.eclipse.org/cdoc-tip/xdc/runtime/Memory.html#alloc

Also you can find more detailed description about Memory_alloc function and examples at the link:

http://rtsc.eclipse.org/docs-tip/Using_xdc.runtime_Memory

Tsvetolin Shulev

0 jason xu over 12 years ago in reply to Cvetolin Shulev-XID

Prodigy 90 points

This issue is resolved by doing the memcpy by resizer: the video frame data is sent to resizer input buffer and resizer just outputs the data to encoder buffer. With this solution, the data is copied by hardware (DMA i think) so the performance is better (only <5ms is needed).

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DM3725 Video Encoding issue