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Thread: TTG and MRV announced for S3 Tivos in November

  1. #46
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    Quote Originally Posted by Jamie View Post
    I don't think tivo->PC will ever be native, since the encryption is completely different on the PC side.
    What you're saying here makes no sense to me. The .tivo file encryption (qualcom encryption) should be happening on the tivo side, otherwise the content is not protected on the wire (unless there's another level of encryption I don't know about). And then it's necessarily the same encryption algorithm on the PC to decrypt.
    The stream itself, whether it's native transport stream, or non-native program stream, should be a separate issue.

    If you look in tivoapp, there's reference to a video/x-tivo-raw-tts content-type. This suggests TTG protocol support for extracting transport streams. It may be as simple as specifying the content-type in the HTML request to get .tivo files with transport stream content.

  2. #47
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    Ok, now that I've actually looked at tivodecoder (I'm new to .tivo format), it looks like .tivo file format assumes mpeg2 ps, and so extracting to a PC in mpeg2 ts was probably not implemented.

  3. #48
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    Quote Originally Posted by bcc View Post
    What you're saying here makes no sense to me. The .tivo file encryption (qualcom encryption) should be happening on the tivo side, otherwise the content is not protected on the wire (unless there's another level of encryption I don't know about). And then it's necessarily the same encryption algorithm on the PC to decrypt.
    The stream itself, whether it's native transport stream, or non-native program stream, should be a separate issue.

    If you look in tivoapp, there's reference to a video/x-tivo-raw-tts content-type. This suggests TTG protocol support for extracting transport streams. It may be as simple as specifying the content-type in the HTML request to get .tivo files with transport stream content.
    Yes, I believe the re-encryption is done on the tivo side, and that's what makes TTG transfers so slow. Anything that is re-encrypted doesn't sound native to me, but perhaps I didn't understand what you meant by "native". I interpreted it as "as stored on disk on the tivo". I thought the point was to avoid any processing on the tivo side to get the highest transfer rates possible. mfs_uberexport is still probably the best bet for that. It's really doing a straight disk to network copy.
    Last edited by Jamie; 10-24-2007 at 09:33 PM.

  4. #49
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    Quote Originally Posted by Jamie View Post
    Yes, I believe the re-encryption is done on the tivo side. Anything that is re-encrypted doesn't sound native to me, but perhaps I didn't understand what you meant by "native".
    s1/s2 boxes store recordings in mpeg2 ps format. s3 boxes store recordings in mpeg2 ts format. By "native" I mean the mpeg2 format in which recordings are stored on the tivo's disk. I think this is what tivopony means as well.
    So, an s2<->s3 transfer involves some stream conversion to switch between formats (non-native transfer). An s3<->s3 or an s2<->s2 transfer can be native. An s3<->pc transfer is apparently always non-native as the tivo server stores the content in a .tivo file which seems to presume mpeg2 ps. I may be wrong - there may be a way to make .tivo files with mpeg2 ts...

    non-native transfers involve extra overhead to convert between formats. For the tivos I think that means some non-trivial performance impact. Ie worth avoiding if possible.

  5. #50
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    Quote Originally Posted by bcc View Post
    ... By "native" I mean the mpeg2 format in which recordings are stored on the tivo's disk. I think this is what tivopony means as well.
    Old style MRV actually copies the ty streams, even the encrypted ones, exactly as they are stored on disk with no processing. You can extract them and diff them and they are identical. The only thing that changes is in the metadata: the CSO/Encryption keys, which are rewritten to map to the different crypto chip.

  6. #51
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    Quote Originally Posted by Jamie View Post
    Old style MRV actually copies the ty streams, even the encrypted ones, exactly as they are stored on disk with no processing. You can extract them and diff them and they are identical. The only thing that changes is in the metadata: the CSO/Encryption keys, which are rewritten to map to the different crypto chip.
    So how does current MRV work? I've never had MRV 'till yesterday and still don't have 2 sub'd ones, so I haven't been able to see it in practice.

  7. #52
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    Quote Originally Posted by bcc View Post
    So how does current MRV work? I've never had MRV 'till yesterday and still don't have 2 sub'd ones, so I haven't been able to see it in practice.
    I'm assuming that "native" MRV is "old style MRV" and "non-native" MRV is the TTG/TTCB protocol. But I haven't spent anytime sniffing network packets yet.

  8. #53
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    Here are some raw netperf numbers I have gotten from my TiVoHD. For reference I've included a S2.5 which I believe runs about 3x faster than stock thanks to the backport drivers. Thanks Jamie, ADH, burbinator and anyone else who made that possible.

    Series2.5, 1000mbps, jumbo frames, custom kernel, agigausb
    Code:
    tivo:/# netperf -H 192.168.168.4 -- -S 65536 -s 65536
    TCP STREAM TEST to 192.168.168.4
    Recv   Send    Send
    Socket Socket  Message  Elapsed
    Size   Size    Size     Time     Throughput
    bytes  bytes   bytes    secs.    10^6bits/sec
    
     65536 131070 131070    10.02      25.52
    Edit: Moved TiVoHD results to soapbox derby.
    Last edited by jkozee; 10-28-2007 at 01:28 AM.

  9. #54
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    Thanks for those results. They are consistent with what I am seeing. The TiVoHD doesn't do as well as the Series3, but is still respectable.

    It might make sense to move further network performance discussions over to the soapbox derby thread.

  10. #55
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    Quote Originally Posted by Jamie View Post
    Quote Originally Posted by bcc
    I thought s3<->s3 MRV was working fine, which is what I meant by s3<->s3.
    Doesn't work for me with the various patches we like to use around here, e.g. to prevent encryption. ...
    I was wrong on this point. Transfers of unencrypted shows works fine for me now, with just the "nocso" patch equivalent. I think I was just testing before I had all the necessary keyring keys -- I had an HM_MAK_... but not an MRV_... key.

  11. #56
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    Quote Originally Posted by Jamie View Post
    I was wrong on this point. Transfers of unencrypted shows works fine for me now, with just the "nocso" patch equivalent. I think I was just testing before I had all the necessary keyring keys -- I had an HM_MAK_... but not an MRV_... key.
    So then, that brings me back to my original question. If MRV on the s3s means "native" mpeg2 ts transfers, then that'd be a big performance win over TTG/TTCB which isn't native for the s3s. If the PC servers could be made to use an MRV-like transfer, they could get the performance win of "native" transfers as well.

  12. #57
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    Quote Originally Posted by bcc View Post
    So then, that brings me back to my original question. If MRV on the s3s means "native" mpeg2 ts transfers, then that'd be a big performance win over TTG/TTCB which isn't native for the s3s. If the PC servers could be made to use an MRV-like transfer, they could get the performance win of "native" transfers as well.
    There's nothing more native than vserver(tivo) to mfs_uberexport(pc). It's a direct disk to network copy. I get >80mbps in s3=>pc transfers that way. "Native" MRV s3<=>s3 transfers are reported on TCF to max out at ~44mbps, and ~21mpbs thd<->thd with stock tivo software. I've personal measured s3<->thd native MRV at ~27mbps sustained, with peaks at ~35mbps, using gige, jumbo frames, custom kernel ,etc. So on a hacked tivo, I'd still recommend hacking extraction tools, if performance is important. On an unhacked tivo, there really isn't the possibility of "native" tivo<->pc transfers, in the sense of no processing on the stream, given the encryption issues previously discussed.
    Last edited by Jamie; 10-31-2007 at 11:48 PM.

  13. #58
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    Lemme start over.
    s3->pc on non-hacked tivo. Uses TTG. Non-native. Slow.
    s3->s3 on hacked or non hacked tivo. Uses MRV. Native (reportedly). "Fast".

    So to make s3->pc faster on non-hacked tivo, change PC servers to use MRV not TTG, or use TTG with mpeg-ts content-type specified.
    May be feasible, would be worth seeing what goes out on the wire for s3<->s3 MRV case.

  14. #59
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    Quote Originally Posted by bcc View Post
    ....So to make s3->pc faster on non-hacked tivo, change PC servers to use MRV not TTG,
    You'd get a stream encrypted with tivos on box encryption, which there is no public way to crack off the tivo.
    ...or use TTG with mpeg-ts content-type specified.
    You'd still have the tivo doing the expensive decrypt/reencrypt, which is what makes TTG slow. It's also not at all clear that tivo included code to do this on the tivo side. Give it a shot, if you feel like it, but I'm not optimistic that you'll see much of a performance improvement.
    Last edited by Jamie; 11-01-2007 at 07:30 AM.

  15. #60
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    Quote Originally Posted by Jamie View Post
    You'd get a stream encrypted with tivos on box encryption, which there is no public way to crack off the tivo.
    Thanks, that'd make sense. I didn't want to assume up front that they did the encryption in a sound manner (using the tivo's private keys). You had said that old MRV copied the ty streams exactly with no processing.
    Oh well nevermind, sorry for the trouble, back to s3tots

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