Skip to content

GitLab

Open
Created by Marianna Smidth Buschle@msb.qtec

Auto-calculation of bitrate bricks Vaapi encoder when framerate=0/1

Create a test file

GST_DEBUG=*:3 gst-launch-1.0 videotestsrc num-buffers=300 ! video/x-raw,format=NV12,width=1920,height=1080,framerate=30/1 ! vaapih264enc rate-control=4 bitrate=20000 ! video/x-h264,profile=high ! filesink location=demo.h264

Transcode it: it works

GST_DEBUG=*:3 gst-launch-1.0 filesrc location=demo.h264 ! queue ! h264parse ! vaapih264dec ! queue ! "video/x-raw,format=NV12" ! queue ! vaapih264enc rate-control=4 bitrate=20000 ! video/x-h264,profile=high ! fakesink -v

Try to trasncode with automatic calculation of bitrate (bitrate=0): it stalls and leaves Vaapi in an un-usable state, requires reboot to recover.

GST_DEBUG=*:3 gst-launch-1.0 filesrc location=demo.h264 ! queue ! h264parse ! vaapih264dec ! queue ! "video/x-raw,format=NV12" ! queue ! vaapih264enc rate-control=4 bitrate=0 ! video/x-h264,profile=high ! fakesink -v

From https://gitlab.freedesktop.org/gstreamer/gstreamer-vaapi/-/blob/master/gst-libs/gst/vaapi/gstvaapiencoder_h264.c#L2707

        base_encoder->bitrate =
            gst_util_uint64_scale (factor, GST_VAAPI_ENCODER_FPS_N (encoder),
            GST_VAAPI_ENCODER_FPS_D (encoder)) / 1000;

So I guess the fps=0 gives a bitrate of zero which breaks the encoder badly.