Something interesting about Tivo2Go transfer rates and Quality settings...

[Puppy76]

I’ve been suspecting this for a long time, but didn’t test it until just now. I didn’t do a super-scientific test, I just timed how long it took to transfer (roughly) 20MB from my Tivo.

Hardware: Humax 590 (should be identical to a Tivo 540, and worse than the 140 and 240 units). All tests were with the Tivo doing nothing but transferring-the live TV buffer was turned off, and no one was watching it.

Results for 20MB:
51s on Basic, which is 401.57KB/s
45s on Medium, which is 455.11KB/s
30s on Best, which is 682.67KB/s
(I haven’t test high yet)

As I suspected, the transfer rate increases-pretty drastically-the higher the quality setting of the show being transferred. (Up to 70% faster.) My theory is that the main bottleneck must be something that’s independent of the bit rate used. Combining two streams into one would probably be equally hard regardless of the bit rate used, so I’m guessing it’s the DRM that gets added to the stream-specifically the speed Tivo’s CPU can add the DRM, that’s the bottleneck to Tivo2Go transfers.

Anyone have any thoughts? Any similar benchmarks?

[Dan203]

DRM is not "added" to TTG files. It's add to the TiVo stream as it's being recorded to hard drive, so it has zero effect on TTG performance.

The reason the throughput is higher with higher quality recordings is because of how multiplexing works. You see in order to keep audio and video sync the multiplexing process must copy a certain number of milliseconds of video data, then a certain number of milliseconds of audio, rinse, repeat. Because of this a video stream with a higher bitrate will have copied more data into the multiplexed stream before the real bottle neck (i.e. the CPU) comes back into play, which inturn results in an increase in over all throughput. However due to the fact that there is more actual data the resulting time frame to transfer the recording is about the same regardless of the recordings quality.

Dan

[Puppy76]

Okay, thanks. I can't believe how knowledgeable you are with this stuff! I had always heard the DRM was added to the files as they left the Tivo, so didn't question that part of it.

Anyway it's kind of interestesting. I had no idea my little Tivo could transfer close to 700KB/s!