[Spice-devel] playbin can't detect vaapi decoder correctly when playing a video stream.

[Qiu Wenbo]

I'm trying to turn on streaming video with H.264 codec manually. I have 
noticed spice-gtk will use playbin to decode the video stream with 
recent gstreamer.  However,  playbin tends to use software decoder 
(avdec_h264) on my box (latest Archlinux running on an Intel i5-6500 PC 
with gstreamer-vaapi). When I remove gstreamer-libav, gstreamer 
complains like this and refuse to setup pipeline:

0:00:00.221423602 4816 0x7f24e40454a0 ERROR h264parse 
gsth264parse.c:2588:gst_h264_parse_set_caps: video/x-h264 caps without 
codec_data or stream-format
0:00:00.221548091 4816 0x7f24e40454a0 ERROR h264parse 
gsth264parse.c:2588:gst_h264_parse_set_caps: video/x-h264 caps without 
codec_data or stream-format
0:00:00.517686292 4816 0x7f24e40454a0 WARN decodebin 
gstdecodebin2.c:2514:connect_pad:<decodebin0> Couldn't set 
vaapidecodebin0 to PAUSED
0:00:00.518742010 4816 0x7f24e40454a0 WARN decodebin 
gstdecodebin2.c:2339:connect_pad:<decodebin0> Element 
vaapidecode_h264-0 does not accept caps
0:00:00.518908940 4816 0x7f24e40454a0 WARN uridecodebin 
gsturidecodebin.c:921:unknown_type_cb:<uridecodebin0> warning: No 
decoder available for type 'video/x-h264, 
pixel-aspect-ratio=(fraction)1/1, width=(int)1920, height=(int)1080, 
framerate=(fraction)30/1, interlace-mode=(string)progressive, 
chroma-format=(string)4:4:4, bit-depth-luma=(uint)8, 
bit-depth-chroma=(uint)8, parsed=(boolean)true, 
stream-format=(string)avc, alignment=(string)au, 
profile=(string)high-4:4:4, level=(string)5, 
codec_data=(buffer)01f40032ffe1001e67f400329184680780227e27016a02020280000003008000001e478c195001000468ce3192'.
0:00:00.518933285 4816 0x7f24e40454a0 WARN decodebin 
gstdecodebin2.c:4640:gst_decode_bin_expose:<decodebin0> error: no 
suitable plugins found:
Couldn't set vaapidecodebin0 to PAUSEDElement vaapidecode_h264-0 does 
not accept caps

0:00:00.518951522 4816 0x7f24e40454a0 WARN uridecodebin 
gsturidecodebin.c:988:no_more_pads_full:<uridecodebin0> error: no 
suitable plugins found:
gstdecodebin2.c(4640): gst_decode_bin_expose (): 
/GstPlayBin:playbin/GstURIDecodeBin:uridecodebin0/GstDecodeBin:decodebin0:
no suitable plugins found:
Couldn't set vaapidecodebin0 to PAUSEDElement vaapidecode_h264-0 does 
not accept caps

However, after install gstreamer-libav, the log shows playbin is using 
avdec_h264. Also, I can confirm playbin is using vaapih264dec when I 
manually change the encoder of spice-server from x264 to vaapih264enc.
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