[Spice-devel] [spice-gtk v1] display-gst: Improve h264 elements filtering

[Pavel Grunt]

On Thu, 2017-07-13 at 14:33 +0200, Victor Toso wrote:
> From: Victor Toso <me at victortoso.com>
> 
> This patch fixes the avdec_h264 element not being present on
> gstvideo_has_codec() which get all decoder elements from GstRegistry
> and filter them on our GstCaps in order to get the ones for given
> codec.
> 
> The issue is around the filtering. The current GstCaps for h264 is not
> consider a subset of avdec_h264's capabilites and that will fiter this
> element out of the list.
> 
> The proposed solution for that is to set `subsetonly` parameter from
> gst_element_factory_list_filter() to false.

that is incorrect for the same reason as my patch (some required element plugin
may be missing)

> 
> While at it, the cap "stream-format=byte-stream" is less useful now
> because it isn't needed to play the stream - see 6fe88871240c53b8
> 
> In my system, our debug shows:
> .. gstvideo_debug_available_decoders: From 228 video decoder elements,
> - 4 can handle caps   image/jpeg: jpegdec, nvdec, avdec_mjpeg, vaapijpegdec

like here a parser for avdec_mjpeg

> - 3 can handle caps  video/x-vp8: vaapidecodebin, vp8dec, avdec_vp8
> - 4 can handle caps video/x-h264: vaapidecodebin, avdec_h264, nvdec,
> vaapih264dec
> - 3 can handle caps  video/x-vp9: vaapidecodebin, vp9dec, avdec_vp9
> 
> Signed-off-by: Victor Toso <victortoso at redhat.com>
> ---
>  src/channel-display-gst.c  | 2 +-
>  src/channel-display-priv.h | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/src/channel-display-gst.c b/src/channel-display-gst.c
> index 20d236a..1bd7df1 100644
> --- a/src/channel-display-gst.c
> +++ b/src/channel-display-gst.c
> @@ -647,7 +647,7 @@ gboolean gstvideo_has_codec(int codec_type)
>      }
>  
>      caps = gst_caps_from_string(gst_opts[codec_type].dec_caps);
> -    codec_decoders = gst_element_factory_list_filter(all_decoders, caps,
> GST_PAD_SINK, TRUE);
> +    codec_decoders = gst_element_factory_list_filter(all_decoders, caps,
> GST_PAD_SINK, FALSE);
>      gst_caps_unref(caps);
>  
>      if (codec_decoders == NULL) {
> diff --git a/src/channel-display-priv.h b/src/channel-display-priv.h
> index 04cb4d1..9bfd4ac 100644
> --- a/src/channel-display-priv.h
> +++ b/src/channel-display-priv.h
> @@ -181,7 +181,7 @@ static const struct {
>       * (hardcoded in spice-server), let's add it here to avoid the warning.
>       */
>      { SPICE_DISPLAY_CAP_CODEC_H264, "h264",
> -      "h264parse ! avdec_h264", "video/x-h264,stream-format=byte-stream" },
> +      "h264parse ! avdec_h264", "video/x-h264" },
>  
>      /* SPICE_VIDEO_CODEC_TYPE_VP9 */
>      { SPICE_DISPLAY_CAP_CODEC_VP9, "vp9",