omxh264enc bitrate low and not configurable

Robotics & Edge Computing Jetson & Embedded Systems Jetson TX2
1

hi

In my application, I use the gstreamer element omxh264enc to encode a 3840x1920P30 video stream. The problem is that the bitrate is incorrectly set to 1~1.2Mbps(from observing running result), not 8Mbps as I set with g_object_set, nor 4Mbps as the default.

g_object_set(G_OBJECT(enc), "bitrate", 8000000, NULL);

The above line of code seems unable to configure encoder’s bitrate, no matter what value it’s set. Only when I set the qp-range property, to lower the max boundry to 30, as

g_object_set(G_OBJECT(enc), "qp-range", "0,30:0,30:0,30", NULL);

the bitrate would go up to somewhere 5Mbps.

Then, to compare, I tried this command line

gst-launch-1.0 \
v4l2src device=/dev/video0 ! 'video/x-raw, width=(int)1920, height=(int)1080, format=(string)UYVY, framerate=(fraction)30/1' ! \
nvvidconv ! 'video/x-raw(memory:NVMM), width=(int)3840, height=(int)1920, format=(string)I420, framerate=(fraction)30/1' ! \
omxh264enc bitrate=8000000 ! h264parse ! mp4mux ! filesink location=./rec.mp4

And this time the bitrate is indeed 8Mbps as expected.

So what’s making the bitrate property invalid?

2

Hi xliu,
Do you configure timestamps correctly in your app? Looks like the frame rate is not 30fps as encoder expects.

3

hi Dane,

The gstreamer pipeline looks like:

appsrc → omxh264enc → h264parse → mp4mux → filesink

The video souce is a live source, but since we need to do some custom processing before encoding, we use appsrc. And I did not set timestamps before feeding buffer to the appsrc element. What to do to add timestamps? Current code uses gst_buffer_new_wrapped_full() and gst_app_src_push_buffer() to do the buffer feeding.

The actual framerate is 30fps, I’m sure of this.

4

hi Dane,

By setting “do-timestamp” of the appsrc, this issue is fixed. Thanks you very much!