[Spice-devel] [PATCH 1/2] server: Don't send stream frames that are identical to the last one

[Yaniv Kaul]

  On 2010-08-26 18:33, Yonit Halperin wrote:
> On 08/25/2010 11:49 AM, alexl at redhat.com wrote:
>> From: Alexander Larsson<alexl at redhat.com>
>>
>> This happens e.g. with the vlc player when paused, as it still draws
>> a continuous stream of frames (bug #28817). It may also help slightly
>> if a video contains identical frames in a row for other reasons.
>>
>> We detect frame equality using the adler32 checksum. There is a small
>> chance of checksum collisions, but that will just cause one frame to
>> be skipped, or if it is the last frame it will be fixed when the stream
>> ends and we get the lossless data for the region.
>> ---
>
> Ack, but I'm not sure we should add efficiency overhead for all 
> streams (audio and video wise) if only VLC behaves in such manner.
> Maybe we can add it only for low bandwidth,  and/or preform sampling 
> of every X frames, and then if they are equal check if all the frames 
> are equal.

I totally agree - right now, it's a corner case (and we should file a BZ 
on VLC to fix their behaviour!)
In addition, IIRC, adler32 is pretty weak for short messages (has a 
greater chance of collisions), making it sub-optimal for the audio 
stream (perhaps fine for the video stream).
Y.

>
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