h264 encoder returns empty packets

[YijinLiu]

Hi,

I have met this bizarre problem. I used ffmpeg with h264_vaapi encoder to transcode a video file on a i7-5557U CPU. It only works alternatively, i.e. it works on 1st, 3rd, 5th times. Other times, it returns empty packets. I compared two run's logs, nothing special from ffmpeg or libva.

I used ffmpeg 4.0.2 and libva/intel-vaapi-driver 2.2.0 on Linux 3.18.36. Here is the command I used: ffmpeg -loglevel 48 -vaapi_device /dev/dri/renderD128 -i test-video.mkv -an -vf 'format=nv12,hwupload' -c:v h264_vaapi test.mkv (You could download the test video here. I don't think it's related to this video though.)

More info:

• It works well with ffmpeg-4.0.2 + libva/intel-vaapi-driver 1.8.3 The problem started from 2.0.0
• So far I could only repro it with i7-5557U on Linux 3.18.36. I cannot repro it with
  • i5-8350U on Linux 4.16.0
  • Celeron N3450 on Linux 4.16.0

I am not sure it's CPU or the kernel. I'll do more test when I could get my hands on other machines.

[YijinLiu]

Update: Cannot repro it with

• i3-4130 on Linux 4.4.0
• i5-5575R on Linux 4.15.0