[Spice-devel] [client v2 1/5] streaming: Document the GStreamer decoding process

[Jonathon Jongsma]

Looks good to me

Acked-by: Jonathon Jongsma <jjongsma at redhat.com>


On Thu, 2017-04-06 at 16:00 +0200, Francois Gouget wrote:
> Signed-off-by: Francois Gouget <fgouget at codeweavers.com>
> ---
>  src/channel-display-gst.c | 26 ++++++++++++++++++++++++++
>  1 file changed, 26 insertions(+)
> 
> diff --git a/src/channel-display-gst.c b/src/channel-display-gst.c
> index c4190b2d..7e0ddde4 100644
> --- a/src/channel-display-gst.c
> +++ b/src/channel-display-gst.c
> @@ -417,6 +417,32 @@ static void release_buffer_data(gpointer data)
>      spice_msg_in_unref(frame_msg);
>  }
>  
> +/* spice_gst_decoder_queue_frame() queues the SpiceMsgIn message for
> decoding
> + * and displaying. The steps it goes through are as follows:
> + *
> + * 1) A SpiceFrame is created to keep track of SpiceMsgIn and some
> additional
> + *    metadata. SpiceMsgIn is reffed. The SpiceFrame is then pushed
> to the
> + *    decoding_queue.
> + * 2) The data part of SpiceMsgIn, which contains the compressed
> frame data,
> + *    is wrapped in a GstBuffer and is pushed to the GStreamer
> pipeline for
> + *    decoding. SpiceMsgIn is reffed.
> + * 3) As soon as the GStreamer pipeline no longer needs the
> compressed frame it
> + *    calls release_buffer_data() to unref SpiceMsgIn.
> + * 4) Once the decompressed frame is available the GStreamer
> pipeline calls
> + *    new_sample() in the GStreamer thread.
> + * 5) new_sample() then matches the decompressed frame to a
> SpiceFrame from
> + *    the decoding queue using the GStreamer timestamp information
> to deal with
> + *    dropped frames. The SpiceFrame is popped from the
> decoding_queue.
> + * 6) new_sample() then attaches the decompressed frame to the
> SpiceFrame,
> + *    pushes it to the display_queue and calls schedule_frame().
> + * 7) schedule_frame() then uses the SpiceMsgIn's mm_time to arrange
> for
> + *    display_frame() to be called, in the main thread, at the right
> time for
> + *    the next frame.
> + * 8) display_frame() pops the first SpiceFrame from the
> display_queue and
> + *    calls stream_display_frame().
> + * 9) display_frame() then frees the SpiceFrame and the decompressed
> frame.
> + *    SpiceMsgIn is unreffed.
> + */
>  static gboolean spice_gst_decoder_queue_frame(VideoDecoder
> *video_decoder,
>                                                SpiceMsgIn *frame_msg,
>                                                int32_t latency)