[Spice-devel] [PATCH spice-server 00/28] adaptive video streaming
Alon Levy
alevy at redhat.com
Sun Apr 14 06:37:22 PDT 2013
On Tue, Feb 26, 2013 at 01:03:46PM -0500, Yonit Halperin wrote:
ACK series, sorry for the delay. I have to admit I don't understand the
first patches as well as I should, but seeing as they have been tested
and that I would just be delaying them further, I prefer to let you push
them. I hope to work a bit on testability of streams that doesn't
require creating a vm, but of course that too is just a note and not
related to acking this series.
> Hi,
>
> The following patch series introduces adaptive video streaming to spice.
>
> Until now, the mjpeg quality was constant (70), and the frame rate was modified
> according to the rate of frame drops in the server side (a drop occurs when a new frame reaches the server while
> an older frame is still queued in the pipe). In the client side, the video playback is synchronized according
> to the audio playback (each audio and video frame holds an mm-time field). The jitter-buffer size in the client
> was constant as well - 100 ms. When video frames arrive late to the client (i.e., when the audio playback is ahead of them),
> they are dropped.
>
> The adaptive video streaming is implemented by the following heuristic:
> Given a bit rate, we calculate the best combination of mjpeg quality and frame rate (henceforth, the stream parameters) for this
> bit rate. In order to decide this combination, we evaluate the encoding size for different jpeg
> qualities by applying them on successive frames.
> Every new stream is assigned with an initial bit rate. The bit rate is re-estimated and
> modified during the stream life time. The bit-rate is modified based on:
> 1) periodic reports from the client:
> The client reports includes information about drops and the playback latency.
> In response to drops, or too short playback latency, we decrease the bit rate.
> In response to reports that suggest that the client playback is stable with the
> current configuration, we try to increase the bit-rate.
> 2) server drops: the bit-rate is decreased when server drops occur.
>
> Each time the bit rate changes, the stream parameters are re-evaluated.
> In addition, we monitor the frames' encoding size, and when there is a change
> that may allow improving the stream parameters, or alternatively, requires decreasing the
> quality, we again re-evaluate them.
>
> Other changes:
> --------------
>
> Besides the client reports, I also added to the protocol a message that controls the
> audio playback latency, for allowing better synchronization of the audio and video playback buffering.
>
> The roundtrip time is used for estimating the required playback delay. In order to get a more accurate estimation
> of the roundtrip time I also added an option to measure it periodically instead of just on startup, and
> take the minimum measurement as estimation.
>
> Results
> -------
> I compared the video quality of the current spice master, and of the new spice, under different network setups.
> Spice master was a bit modified for making the comparison more fair: I increased the audio jitter buffer to 200ms (instead of 100),
> and also included the patch "red_worker: stream agent - fix miscounting of frames".
> The network setup was emulated using tc.
>
> You can find the tests details and the results in a following email.
>
> For 5Mpbs and 60ms roundtrip (Test1), in spice-master, more than 70% of the frames that are sent to the client are being dropped, and the video
> is unwatchable. With new spice, while the average frame rate is about the same, only about 2% of the frames are being dropped by the client.
> For 2.5Mbps and 60ms (Test2), as expected, things gets worse for spice-master, and the drops rate reaches 90%. For the new spice, it is less then 20%, and
> the video is watchable.
>
> I also tested a setup of 10Mbps with high latency (170ms, Test3). The latency affects the initial bit rate estimation in spice (probably due to the tcp acks overhead).
> Thus, the stream is started with a bit-rate estimation of less then 1.25Mbps. The adaptive video heuristic gradually converges to a higher bit rate (the column "end-bit-rate"), and
> the next video stream will be started with the improved bit rate estimation.
> In Test5 I tested a real environment with a network setup similar to Test3. However, the test are not comparable because in Test5 setup (different server and guest),
> the basic frame rate (i.e., from the guest to the server) is much smaller (still need to investigate why).
>
> In Test4 (20Mbps; <1 ms roundtrip), I evaluated and unlimited setup, i.e., a setup which will allow the best frame rate and jpeg-quality for the stream.
> With new spice, the capacity of the channel is exploited efficiently. With spice-master, the condition for dropping frames according to the defined fps is too strict,
> and the observed frame rate is smaller then the maximum possible.
>
> Video streaming short-term TODO:
> ----------------
> - Implement playback-latency adjustments for spice-gtk gstreamer front-end.
> - Add vp8 encoding
> - Solve some problems we have with video identification.
> - Try to achieve faster convergence to the "right" bit-rate when we start with a wrong estimation.
>
> long-term TODO:
> ---------------
> video pass-through
>
> Regards,
> Yonit.
>
> Yonit Halperin (28):
> red_worker: stream agent - fix miscounting of frames
> server/red_worker: streams: moving mjpeg_encoder from Stream to
> StreamAgent
> mjpeg_encoder: configure mjpeg quality and frame rate according to a
> given bit rate
> mjpeg_encoder: re-configure stream parameters when the frame's
> encoding size changes
> mjpeg_encoder: adjust the stream bit rate based on periodic client
> feedback
> mjpeg_encoder: modify stream bit rate based on server side pipe
> congestion
> mjpeg_encoder: update the client with estimations for the required
> playback latency
> mjpeg_encoder: move the control over frame drops to mjpeg_encoder
> mjpeg_encoder: keep the average observed fps similar to the defined
> fps
> mjpeg_encoder: add stream warmup time, in which we avoid server and
> client drops
> server: spice_timer_queue
> server/red_worker: assign timer callbacks to worker_core, using
> spice_timer_queue
> red_channel: monitor connection latency using MSG_PING
> red_worker: stream - update periodically the input frame rate
> server/red_worker: enable latency monitoring in the display channel
> red_worker: start using mjpeg_encoder rate control capabilities
> red_worker: support SPICE_MSGC_DISPLAY_STREAM_REPORT
> red_worker: notify mjpeg_encoder on server frame drops
> red_worker: ignoring video frame drops that are not due to pipe
> congestion
> dispatcher.h: fix - s/#define MAIN_DISPATCHER_H/#define DISPATCHER_H
> snd_worker: support sending SPICE_MSG_PLAYBACK_LATENCY
> reds: support mm_time latency adjustments
> red_worker: video streams - adjust client playback latency
> server/red_worker.c: use the bit rate of old streams as a start point
> for new streams
> server/red_worker: add an option to supply the bandwidth via env var
> collect and print video stream statistics
> red_worker: increase the interval limit for stream frames
> red_worker: assign mm_time to vga frames
>
> server/Makefile.am | 2 +
> server/dispatcher.h | 6 +-
> server/inputs_channel.c | 1 +
> server/main_channel.c | 7 +-
> server/main_channel.h | 1 +
> server/main_dispatcher.c | 32 ++
> server/main_dispatcher.h | 2 +
> server/mjpeg_encoder.c | 981 ++++++++++++++++++++++++++++++++++++++++++++-
> server/mjpeg_encoder.h | 70 +++-
> server/red_channel.c | 228 +++++++++++
> server/red_channel.h | 18 +
> server/red_dispatcher.c | 1 +
> server/red_worker.c | 514 +++++++++++++++++++-----
> server/reds-private.h | 2 +
> server/reds.c | 28 +-
> server/reds.h | 2 +
> server/smartcard.c | 1 +
> server/snd_worker.c | 45 +++
> server/snd_worker.h | 2 +
> server/spice_timer_queue.c | 268 +++++++++++++
> server/spice_timer_queue.h | 43 ++
> server/spicevmc.c | 1 +
> spice-common | 2 +-
> 23 files changed, 2148 insertions(+), 109 deletions(-)
> create mode 100644 server/spice_timer_queue.c
> create mode 100644 server/spice_timer_queue.h
>
> --
> 1.8.1
>
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