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Common Issues

7. Rockchip Platform Support​

7.14 Common Issues​

7.14.1 4K30 Plays Normally but 4K60 Stutters​

  1. Confirm that mppvideodec, rather than a software decoder, is actually being used.
  2. Test the frame rate from the decoder to fakesink and from the decoder to the display sink separately.
  3. Use --flags=3 to disable subtitles.
  4. Check the CPU, GPU, and VPU frequencies, system load, and DDR bandwidth.
  5. Compare performance with AFBC when the entire path supports it.
  6. Test sync=false only when measuring throughput; clock synchronization should normally remain enabled during playback.

7.14.2 High CPU Usage​

Common causes include not using MPP hardware decoding, software format conversion, or high processing overhead from subtitles and scaling. Use GST_DEBUG and a DOT graph to confirm which decoder was actually created and whether videoconvert was inserted.

7.14.3 Playback Stalls or Progress Remains at 0​

First try Playbin3:

gst-play-1.0 --flags=3 --use-playbin3 test.mp4

Also use gst-discoverer-1.0 to check the container, tracks, and missing plugins.

7.14.4 Video Is Displayed but There Is No Audio​

First use aplay to verify the sound card, and then specify the ALSA device explicitly:

gst-play-1.0 --flags=3 test.mp4 \
  --audiosink='alsasink device=hw:0,0'

7.14.5 Subtitles Cause Stuttering​

Subtitle composition may involve image extraction, RGB conversion, blending, and conversion back to the display format. Use --flags=3 to disable subtitles during performance tests. For high-resolution products, consider drawing subtitles on a separate layer with a UI framework such as Qt.

7.14.6 v4l2src Cannot Capture at the Full Frame Rate​

First bypass GStreamer to verify the V4L2 driver capability:

v4l2-ctl -d /dev/video0 \
  --set-fmt-video=width=1920,height=1080,pixelformat=NV12 \
  --stream-mmap=3 --stream-skip=1 --stream-poll

If v4l2-ctl reaches the full frame rate but GStreamer does not, increase the number of buffers:

gst-launch-1.0 v4l2src device=/dev/video0 min-buffers=64 \
  ! 'video/x-raw,width=1920,height=1080,format=NV12' \
  ! waylandsink

Also confirm that the downstream path is not blocked, and add a queue before branches such as encoding and display.

7.14.7 v4l2src Format Negotiation Fails​

v4l2-ctl -d /dev/video0 --list-formats-ext
gst-inspect-1.0 v4l2src
  • When the device outputs a raw format such as NV12, NV16, BGRA, or BGRx, connect it to a display or encoding plugin that supports the same Caps.
  • When the device outputs JPEG/MJPEG, add jpegparse ! mppjpegdec.
  • When the upstream and downstream formats do not match, add videoconvert, while accounting for the CPU or RGA overhead.

7.14.8 Resolutions Above 4K Cannot Be Captured​

Check the limit in /etc/profile.d/gst.sh:

export GST_V4L2SRC_MAX_RESOLUTION=3840x2160

If the hardware, driver, and bandwidth all support the required resolution, increase this value as needed and reload the environment.