Video Streaming¶
This section contains different simulations in a video channel setting.
We model this with several packets being sent simultaneously and a transfer-delay is added to simulate a frame-rate of a video stream.
In video streaming packet loss is a visible quantity as it results in video glitches. When a frame is lost, information and pixels are lost in the image. Delayed receival of packets results in buffering, lowered resolution or skipped frames.
The latency and residual packet loss are therefore important parameters to minimize in order to maximize the Quality of Service.
Therefore, in video streaming, the main focus is to answer the two questions:
- How much of the packet loss is fixed?
- How delayed are the packets?
In order to ensure the realism in terms of delay, we have imposed a latency-budget (latency-constraint), that the codecs have to comply with. Otherwise, the packet exceeding the budget will be considered lost.
What do we expect?¶
In general, we expect Rely to perform better than all of the other codecs in terms of both parameters. You can find setups where the other codecs have an upper hand, however, these are highly situational and Rely beats them in the majority of realistic setups.
Residual packet loss:
Rely has an upper hand against the general FEC codecs (Reed-Solomon, Parity2D) with it’s Content-Aware settings (See Content-Aware-Coding).
The general FEC codecs are block codes. Block codes are memoryless, meaning that if a packet is lost after the code attempts to correct it, the packet is lost.
Rely has memory of a ‘window’ of packets, giving it more leeway to fix an unlucky situation, where too many packets were lost.
Given the latency-budget, we expect Rely to outperform ARQ. Especially with increasing packet loss.
ARQ actively trades latency for reliability, so constraining this will hurt the protocol, while Rely adds negligable delay in almost all cases.
Latency:
In order to level the residual loss playing-field, we have allowed the FEC algorithms to operate on larger repair intervals than Rely.
This is an active trade of latency for reliability for block codes. Hence Rely will most likely outperform these.
ARQ is suspected to add more latency than Rely, as Rely will fix most lost packets without needing time-costly retransmissions.
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