Packet Loss Sensitivity - Streaming
So with these test files in hand, I then both streamed and played them while trying different packet loss settings in the Linktropy 4500. I started out with a 1% packet loss rate with a streamed file and found blockiness right of the bat. I then ran a series of tests summarized in Tables 1 through 3 below. You'll have to forgive the use of subjective descriptions in the results, but it was the best way that I could characterize what I found.
I've also included some screen captures of error rates, so that you can get a feel for what I was seeing.
Table 1: VOB file stream results
| Packet Loss | Result |
|---|---|
| 5% | unwatchable |
| 1% | unwatchable |
| 0.5% | borderline watchable with blockiness |
| 0.25% | watchable, with frequent small blocky glitches |
| 0.1% | watchable, with less frequent small blocky glitches |
| 0.05% | watchable, with occasional small blocky glitches |
Figure 10: Streamed VOB file with 5% packet loss (image © Disney, click to enlarge)
Table 2: DivX file stream results
| Packet Loss | Result |
|---|---|
| 5% | unwatchable, video and audio breakups |
| 1% | unwatchable. Constant large blockiness |
| 0.5% | borderline watchable with blockiness |
| 0.25% | watchable, with frequent small blocky glitches |
| 0.1% | watchable, with less frequent small blocky glitches |
| 0.05% | watchable, with occasional small blocky glitches |
Figure 11: Streamed DivX file with 1% packet loss (image © Sony Pictures, click to enlarge)
Table 3: PSP / MPEG4 file stream results
| Packet Loss | Result |
|---|---|
| 5% | unwatchable and player locks up |
| 1% | unwatchable, but player doesn't lock up |
| 0.5% | borderline watchable |
| 0.25% | watchable, with occasional glitches |
| 0.1% | watchable, with occasional glitches |
| 0.05% | watchable, with a few glitches |
Figure 12 shows a particularly nasty glitch encountered with a 0.05% packet loss. So even when the glitches were infrequent, they could still be pretty nasty!
Figure 12: Streamed PSP/MPEG4 file with 0.05% packet loss (image © Disney)
My general conclusions from the streaming tests are:
it doesn't take much packet loss to introduce problems into streamed video bit rate and encoding format don't make much difference in a stream's ability to compensate for packet loss errors