capture video frame shakes

Naveen Kumar62512

I am in the process of setting up a full-duplex video phone on OMAP L138 
(hawkboard).

I am running H.264 enc/dec on the DSP and the ARM is running Linux 
kernel v2.6.33. I am using QCIF resolution for video capture/display.I 
am using v4l2 driver for capture and fbdev driver for display. ARM and 
DSP communicate via DSPLINK using PROC_read/PROC_write .

I have two hawkboards and able to send and receive frames between the 
evm via ethernet. However, I am noticing frame shaking and stripes of 
lines in the captured frame (before feeding to encoder) whenever encoder 
is enabled. If I disable the encoder, then the captured frame does not 
shake or has any lines. Except for this issue, the overall program is 
working fine and I get 25 FPS throughput most of the times and 
occasionally it dips to 22 FPS.

What is causing the shaking or stripes of lines? Am I missing any real-time deadlines? I am 
assuming that the DSP has full control of DMA resources -- is this correct?

Please let me know if there is anything obvious that I should be looking at.

over 14 years ago

0 tlee over 14 years ago

TI__Guru 62975 points

Naveen,

I'd recommend setting some flags in your enc/dec algorithm that are read when you service the video interrupts. It's possible that the enc/dec is not keeping up with the frame rate.

Since the video port is designed to capture/output frames at a constant rate, on-the-fly changes in enc/dec performance can produce problems.

-Tommy

0 Naveen Kumar62512 over 14 years ago in reply to tlee

Prodigy 70 points

Thanks for the reply.

Encoder and decoder are not serviced as interrupts. I capture video frame on ARM and write it dsp memory using proc write . Also set a flag(uncacheble) on dsp side from ARM. DSP waits for this flag to be set. If set it encodes or decodes depending on the case. My problem is if I enable encode, even the captured frame is shaky. If I skip process call of encoder, the captured frame doesn't exhibit this behavior.

Another similar issue, audio works fine separately. But if run it with video, each read/write to sound fd takes a lot of time. The problem disappears if encoder process call is commented out... In short my observation is encoder interferes with drivers. One known assumption in the encoder lib is that edma is entirely available to it (open,assign,trigger,wait programmed inside lib). Is that valid? Do these drivers use dma resources for any data transfers? If yes, how can I find out what channels they use? am i missing out anything else related to peripherals.?

0 Naveen Kumar62512 over 14 years ago in reply to Naveen Kumar62512

Prodigy 70 points

I replaced edma with cpu copy in both encoder and decoder lib. There is no shaking problem. But the frame rate is very low.

I came across a edma resource allocation thread bw arm and dsp in the following links.

http://e2e.ti.com/support/dsp/omap_applications_processors/f/42/t/63377.aspx

In one of the posting they talk about the edma kernel files arch / arm / mach-davinci / include / mach / edma.h and arch / arm / mach-davinci / devices-da8xx.c.

The links are http://arago-project.org/git/projects/?p=linux-omapl1.git;a=blob;f=arch/arm/mach-davinci/include/mach/edma.h;h=55e217eb9536144a39de21be774056050e817a9b;hb=82684a40f09165c00ca1a8e1a125ebd7885a9960

http://arago-project.org/git/projects/?p=linux-omapl1.git;a=blob;f=arch/arm/mach-davinci/devices-da8xx.c;h=88921c1ef4ebe9b461d99c7672d843997affc58a;hb=82684a40f09165c00ca1a8e1a125ebd7885a9960

How modify these files to make linux use only cc1. Is it possible? In devices-da8xx.c what are slots?

0 tlee over 14 years ago in reply to Naveen Kumar62512

TI__Guru 62975 points

Naveen,

I moved this thread to the Linux forum so they can address your driver/kernel resource questions.

-Tommy

Processors

Processors forum

capture video frame shakes