Tvheadend

Hi,
I'm using the latest TVHeadend 4.2.7 on a AlpineLinux based system. I'm trying to transcode a stream by using the hardware VAAPI transcoder (I have an Intel N4200 CPU), but it seems to be failing in TVHeadend.

The errors I'm getting are these:

hevc_vaapi: H.265/HEVC (VAAPI):
2018-12-06 15:34:13.662 transcode: 000A: 1:H264 1920x1080 ==> HEVC 1920x1080 (hevc_vaapi)
2018-12-06 15:34:13.662 transcode: 000A: 2:AAC-LATM ==> Passthrough
2018-12-06 15:34:13.688 transcode: 000A: Using preset medium
2018-12-06 15:34:13.688 libav: Specified pixel format yuv420p is invalid or not supported
2018-12-06 15:34:13.688 transcode: 000A: Unable to open hevc_vaapi encoder
2018-12-06 15:34:14.671 libav: Using AVStream.codec to pass codec parameters to muxers is deprecated, use AVStream.codecpar instead.

h264_vaapi: H.264/AVC (VAAPI):
2018-12-06 15:36:37.885 transcode: 000B: 1:H264 1920x1080 ==> H264 1920x1080 (h264_vaapi)
2018-12-06 15:36:37.885 transcode: 000B: 2:AAC-LATM ==> Passthrough
2018-12-06 15:36:37.904 transcode: 000B: Using preset medium
2018-12-06 15:36:37.905 libav: Specified pixel format yuv420p is invalid or not supported
2018-12-06 15:36:37.905 transcode: 000B: Unable to open h264_vaapi encoder
2018-12-06 15:36:38.856 libav: Using AVStream.codec to pass codec parameters to muxers is deprecated, use AVStream.codecpar instead.

vp8_vaapi: VP8 (VAAPI):
2018-12-06 15:39:00.538 transcode: 000C: 1:H264 1920x1080 ==> VP8 1920x1080 (vp8_vaapi)
2018-12-06 15:39:00.538 transcode: 000C: 2:AAC-LATM ==> Passthrough
2018-12-06 15:39:00.561 libav: Specified pixel format yuv420p is invalid or not supported
2018-12-06 15:39:00.561 transcode: 000C: Unable to open vp8_vaapi encoder
2018-12-06 15:39:01.521 libav: Using AVStream.codec to pass codec parameters to muxers is deprecated, use AVStream.codecpar instead.

Running VAINFO shows this:

vainfo
error: can't connect to X server!
libva info: VA-API version 1.2.0
libva info: va_getDriverName() returns 0
libva info: Trying to open /usr/lib/dri/i965_drv_video.so
libva info: Found init function __vaDriverInit_1_2
libva info: va_openDriver() returns 0
vainfo: VA-API version: 1.2 (libva 2.2.0)
vainfo: Driver version: Intel i965 driver for Intel(R) Broxton - 2.2.0
vainfo: Supported profile and entrypoints
      VAProfileMPEG2Simple            : VAEntrypointVLD
      VAProfileMPEG2Main              : VAEntrypointVLD
      VAProfileH264ConstrainedBaseline: VAEntrypointVLD
      VAProfileH264ConstrainedBaseline: VAEntrypointEncSlice
      VAProfileH264ConstrainedBaseline: VAEntrypointEncSliceLP
      VAProfileH264Main               : VAEntrypointVLD
      VAProfileH264Main               : VAEntrypointEncSlice
      VAProfileH264Main               : VAEntrypointEncSliceLP
      VAProfileH264High               : VAEntrypointVLD
      VAProfileH264High               : VAEntrypointEncSlice
      VAProfileH264High               : VAEntrypointEncSliceLP
      VAProfileH264MultiviewHigh      : VAEntrypointVLD
      VAProfileH264MultiviewHigh      : VAEntrypointEncSlice
      VAProfileH264StereoHigh         : VAEntrypointVLD
      VAProfileH264StereoHigh         : VAEntrypointEncSlice
      VAProfileVC1Simple              : VAEntrypointVLD
      VAProfileVC1Main                : VAEntrypointVLD
      VAProfileVC1Advanced            : VAEntrypointVLD
      VAProfileNone                   : VAEntrypointVideoProc
      VAProfileJPEGBaseline           : VAEntrypointVLD
      VAProfileJPEGBaseline           : VAEntrypointEncPicture
      VAProfileVP8Version0_3          : VAEntrypointVLD
      VAProfileVP8Version0_3          : VAEntrypointEncSlice
      VAProfileHEVCMain               : VAEntrypointVLD
      VAProfileHEVCMain               : VAEntrypointEncSlice
      VAProfileHEVCMain10             : VAEntrypointVLD
      VAProfileVP9Profile0            : VAEntrypointVLD

Also running ffmpeg manually with vaapi works correctly with this command:

ffmpeg -vaapi_device /dev/dri/renderD128 -hwaccel vaapi -hwaccel_output_format vaapi -i input.ts -an -vf 'format=nv12|vaapi,hwupload' -c:v h264_vaapi -qp 25 output.mp4

Is there something special that has to be enabled in order to have a working VAAPI profile to use Hardware transcoding in TVHeadend? Or is there any way to manually specify a piped command for transcoding in TVHeadend?