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Thread: ExtractStream and PlayStream failing on every sector in a DTivo

  1. #76
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    Dec 2001
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    37
    If it is DSS transport stream, it will be 147 bytes. Take a look at the links I posted on the first page of this thread.

    Somebody posted shortly afterwards that the DTivo did 'not' save transport stream packets. Of course what do they know.

    Anyhow, there should be the streamid and a byte, followed by payload data 127 bytes, followed by 17 bytes of error correction or whatnot. Inside that you should see the standard MPEG packets.

  2. #77
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    Dec 2001
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    MPEG2 streams have video packets starting with 0, 0, 1, E0.. so they're easy to find. If these packets always start right after the same 3 byte code, you know you have a DSS transport stream. If not, it's likely normal MPEG2.

    MPEG2 program streams are formatted into 2048 byte 'pack' packets which always start with a 0, 0, 1, BA packet id. They're easy to find too. If you find one of these every 2048 bytes, you know you've got a standard formatted MPEG stream.

    If you find the E0 video packets but no BA pack packets, and no regular 3 byte header in 147 byte intervals, you've got some sort of nonstandard streaming packet file or whatnot.

  3. #78
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    Dec 2001
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    A dish 5000 with an 8vsb modulator plugin can output raw digital HD from Dish network, allowing you to record HD files. However no such capabilities are to be found in any of DirecTV's hardware. Tuning to HDNet on DirectTV, recording in the background, then plugging the drive into the pc and stripping the data seems like the easiest way. BTW, it'd take about 5-7 hours to grab a typical HD movie off the TivoNET through 10Mbps ethernet. Swapping drives is the only way unless someone can figure out how to cram a 100 card in there.

  4. #79
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    Sep 2001
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    I've seriously considered setting up a drive with ext2 and plugging it in to my single drive TiVo and using that as a transport..

    .. a 20Mbit connection should get us going in realtime...

    .. to really do in nice, an external cpu with the ethernet and some kind of dma controller would be needed..

  5. #80
    Join Date
    Jan 2002
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    Eightysix:
    I'd missed those links early on, great info! I'm fairly sure (from conversations with TiVo folk) that the DTiVo does indeed write decrypted (by the H/HU card) transport stream to disk, though it's possible that it's just writing elementary streams, that seems unlikely. SA's store TS, right? So why wouldn't a DTivo?

    Whether that changed or got another layer of encryption in 2.5 remains to be seen.

    I actually have a Dish5000/HDTV Mod/HiPix combo and love it. The only thing I can't do right now is record HDNet from Direct.

    Trying to get a DTiVo to record HDNet is a fairly high priority for me, and I agree that the right answer is to physically move the drive to another machine. I'm suddently envisioning hacking the DTivo into a PC case to get a drive bay for a removable sled. Doesn't seem very elegant unless I get some cool aluminum-and-glass case.

    Either that, or write a cron job to do the transfers when I'm not recording something else, I doubt I'd really want to get more than 1-2hrs of programming a day off HDNet, they repeat a lot of content.

    Of course, then I'll have to find or hack together a utility to pad out the extracted HD to a 19.4Mbps ATSC-legal stream to keep the HiPix happy for playback. Eightysix: Do you have any good references on ATSC?

  6. #81
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    Nov 2001
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    117
    I think I'm getting a little out of my depth of expertice in reviewing the mpeg/tystream internal contents. I think some other group members are a bit more on top of this, so I dumped with dd the first 100K of each of the 4 extractions that I did. I'm posting them here so help facility the process for the group, hopefully someone can make the determination as to the contents.
    Did I do that...

  7. #82
    Join Date
    Sep 2001
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    889
    The streams seem to be compatable with the video stream editors found here http://ddc.mahns.com/se.html

    Theres no regularly spaced packets of any kind..

    There ARE sequentially numbered packets
    00000101
    00000102
    00000103
    00000104
    00000105
    ...
    0000011F

    and there are other packets too..
    000001C0 is a common one...


    .. so.. it IS mpg, and is NOT transport layer

  8. #83
    Join Date
    Jan 2002
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    Toronto
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    OK, so not knowing much about MPEG internals, what does this mean as far as creating a conversion tool goes? Does this mean it should be relatively easy?

  9. #84
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    Jan 2002
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    Im just thinking, (newbie here so correct me if I'm wrong) is it possible to replay shows recorded earlier without the use of the access card? If so then that would eliminate the possibility of the recorded video from being encrypted wouldn't it?

  10. #85
    Join Date
    Jul 2001
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    426
    The 2.0 Variable rate streams play back oddly because there appear to be no time indexes in the audio stream segment. (That may be why playback speeds end up distorted.) On the fixed rate streams there are regular time stamps on both audio and video. On the variable rate there appears to indexes on the video only, but they are not a simple progression. Often the first index of a chunk has a diffrent seq index then the other records in the chunk.

    Tystream appears to parse the video ok, even if it complains about the indexes, it should be possible to create a matching audio index, since this is a muxed stream.

    Good luck on the 2.5 streams.

  11. #86
    Join Date
    Dec 2001
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    17
    tivomon: Just to be clear, the streams you posted are from 2.0.1, not 2.5, right? The reason I ask is that the streams I've been extracting from 2.5 look nothing like the one you posted. There is very little "whitespace" or zeroed-out regions in my files, and they look very random, or encrypted.

    Can anyone else who's used mfs_export or Dx1 on 2.5 report similar results?

    -Ray

  12. #87
    Join Date
    Nov 2001
    Posts
    117
    rwaldn,

    The streams I posted came from a D-Tivo running factoy 2.0.1 and prom version 1.10. If need I can load xtreme2.5 and we can run another extraction under 2.5 and see what's happening there.
    Did I do that...

  13. #88
    Join Date
    Jun 2001
    Location
    Dallas
    Posts
    588
    I was thinking about the easiest way to get the data off the drive. ZapTivo probalby has the most base work done on it and it has the source. Shouldn't be too hard to get it to copy the streams out that it finds instead of writing zero's over them. Probably will have to fix it's mechanism for finding the streams because it doesn't currently work with DTivo. Any thoughts from the programming guru's out there?
    Information wants to be free....

  14. #89
    Join Date
    Nov 2001
    Posts
    117
    I tried a few opensource utils like xmpeg, tpmnc and mpgx and still I'm not able to have anything reconize this as a mpeg file. Maybe I just have a basic mis-understanding of that. In any event I'm going thru http://ddc.mahns.com/se.html to get a better picture of what I should expect in the file. Also look at this in a hex editor I'm seeing the hex digits "dead beef" reocurring many times in the file. Is there any significance to this ?
    Did I do that...

  15. #90
    Join Date
    Dec 2001
    Posts
    37
    The streams seem to be compatable with the video stream editors found here http://ddc.mahns.com/se.html

    Theres no regularly spaced packets of any kind..

    There ARE sequentially numbered packets
    00000101
    00000102
    00000103
    00000104
    00000105
    ...
    0000011F

    and there are other packets too..
    000001C0 is a common one...


    .. so.. it IS mpg, and is NOT transport layer
    Not so fast. Remember that the regular MPEG packets are actually embedded inside the transport stream packets, so you'll find these packet id's in the "payloads" of the DSS transport packets. Of course these tags are a good indicators of where the transport packets start if you find them.. just move a few bytes before and check for transport packet bytes.

    I know for a fact that DirecTV is 'not' 188 byte MPEG2 packets, it is 147 byte DSS packets. Dish is 188, and so is over the air HDTV.

    To find the ATSC spec, just go to their web site www.atsc.com. They have all of the specs online.

    To find the MPEG2 spec (at least the transport spec), you have to search for it I guess. I think you might have to pay for it, but you might find some information on it by searching google for pdf files for is138181 or ISO/IEC 13818-1.

    To check if it's a DSS transport stream, check the three bytes right before the 000001E0 and 000001C0 codes to see if they are constantly the same three bytes. If they are, it's likely that these bytes are the DSS transport stream link header, and that we have either a 127 byte DSS packet or 147 byte DSS packet with the 17 bytes of trailing error correction data.

    The way to check if it's a standard program stream is to look for pack codes 000001BA. This packet will start at the beginning of every 2048 byte chunk in a normal program stream file. If this is not there, the data is NOT in standard MPEG2 format. If it's not a transport stream, it's likely an interleaved set of 'raw' MPEG2 packets.

    To convert from a DSS transport stream, you need to gather all of the 147 byte packets for a given stream, then starting with the first packet marked as 'start', extract all the packet's payloads into a single MPEG2 packet. Then you have to split this packet up into 2048 byte 000001BA packets for the MPEG2 program stream, and pad the last 'pack' packet with a 000001BE padding packet.

    You have to do the same for raw MPEG2 streams if they're not formatted in 2048 byte chunks starting with a 000001BA pack chunk.
    Last edited by eightysix; 01-13-2002 at 02:38 AM.

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