GNOME Bugzilla – Bug 786802
vaapidecode: h264: fix nal aligned streams
Last modified: 2018-11-03 15:51:17 UTC
Running the following pipeline: gst-launch-1.0 filesrc location=CI_MW_D.264 ! h264parse ! video/x-h264, stream-format=byte-stream, alignment=nal ! vaapih264dec ! vaapisink seems to show only a single frame while the pipeline works correctly with au alignment: gst-launch-1.0 filesrc location=CI_MW_D.264 ! h264parse ! video/x-h264, stream-format=byte-stream, alignment=au ! vaapih264dec ! vaapisink A quick workaround seems to be to not mark the GST_H264_NAL_AU_DELIMITER units as AU and FRAME START which makes the above pipeline work but the problem still persists for other files such as BAMQ1_JVC_C.264. Files from ITU-T_H.264.1(2016-02)_AVCv1_bitstreams.zip from https://www.itu.int/net/itu-t/sigdb/spevideo/VideoForm-s.aspx?val=102002641.
Setting the priority as High since the "aligname=nal" should be considered as the default format of h264 and which should work with vaapih264dec.
I've looked into this issue all this week. This is a bit tricky but let me try to explain briefly. 1. This is introduced by my commit to gsth264parse (201e71c in gst-plugins-bad) Since the commit landed, incoming data with byte-stream/nal is like: <AU><SLICE> instead of just only <SLICE>. vaapih264dec can't handle this now, which is this issue. 2. I think vaapih264dec is doing fine in the way it should do. Adding AU to a frame and adding SLICE to the frame (by add_to_frame) and have_frame call. 3. Meanwhile, in the base video decoder, it tries to decide frame information such as pts, duration, etc. See gst_video_decoder_get_buffer_info_at_offset. Previously it choose info from slice buffer properly, but for now it choose from AU buffer. Finally this wrong information leads to dropping all frames in gst_video_decoder_clip_and_push_buf. Acutally, I tried to improve gst_video_decoder_get_buffer_info_at_offset, but I realized that I have to be careful since there are lots of cases. Now I'm looking for other solution. :(
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