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Converting .tivo to .mp4

Discussion in 'TiVo Home Media Features & TiVoToGo' started by narbertb, Feb 2, 2008.

  1. ggieseke

    ggieseke Active Member

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    You can save files as .TiVo or straight MPEG-2, but that still won't make a DVD that will work in most players. You need DVD "authoring" software to create the menus, VOB files, etc. NeroVision Express can handle that part of the job but I don't think it comes with the version of Nero that's usually bundled with some PCs.

    VRD TVSuite includes its own authoring package and you can burn the image directly or save it to disk and burn with something else.

    In my experience, 90 minutes is just about the limit for a single layer (4.7GB) DVD. Two average 1 hour shows with the commercials removed is just right.
     
  2. dlfl

    dlfl Cranky old novice

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    V1 and V2 process several formats of MPEG2 PS (Program Stream) video, including .mpg, .tivo, .vob and .dvr-ms. Thus specifically, you can input and/or edit .tivo and output any of those formats.

    When you set up a DVD in V2 or V3 it will tell you whether your video content fits on a single- or dual-layer DVD. DVD output can be files (ISO or Video_TS) that can be burned to DVD using separate burner software (e.g., imgburn) or VRD will burn directly to the DVD.
     
  3. unitron

    unitron Active Member

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    I'm unfamiliar with the experience of buying or owning a new PC.

    Whatever versions of Nero I have came with new DVD decks I bought and installed in old PCs I've cobbled together.

    So a single layer DVD, which I assume is the first version released, wasn't big enough for a single 2 hour movie?
     
  4. dlfl

    dlfl Cranky old novice

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    SL DVD holds 4.7GB which, for a 2 hr video, computes to an average bitrate of about 5.2Mbps, which must include audio and other overhead. This can provide decent PQ but you probably have to recode the video to this bitrate (and to DVD resolution, if not already there). V2 or V3 automatically recode for resolution when making a DVD image. It's been a while since I used it to make a DVD but I think you can adjust parameters on the recode that is implicit to making the DVD to fit 2 hrs into a SL DVD. If not you might have to do a separate recode in VRD to get a .mpg of the proper size (i.e., reduced bitrate) and dimensions.
     
  5. Soapm

    Soapm Active Member

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    So close,...
    Do a search for DVD shrink and you can put a 4 hour movie on a single layer. You can go down in quality until there's not enough beer to make the show viewable.
     
  6. dlfl

    dlfl Cranky old novice

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    Now that's what I call a practical metric for PQ!
     
  7. ggieseke

    ggieseke Active Member

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    :D
     
  8. unitron

    unitron Active Member

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    Before there were recordable DVD blanks, as I dimly recall, there were commercially available manufactured DVDs with stuff that had aged out of movie theaters and off of HBO.

    Could a single one of those not accommodate a 120 minute movie?
     
  9. ggieseke

    ggieseke Active Member

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    All of the commercial DVDs that I've seen are dual-layer, so they can hold about 3 hours.
     
  10. wmcbrine

    wmcbrine Ziphead

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    Back when I used to rip a lot of DVDs, I found that the majority of them were encoded to just fit on a single-layer disc. This was true even when the disc itself was dual-layer -- the main title was kept under 4.7 GB, while the remaining space was given over to extras. I assume this was done to allow mastering a single-layer version without extras.

    And when I used to make DVDs from DirecTiVo Series 2 recordings, I could typically get about three movies onto a single-layer disc.
     
  11. lrhorer

    lrhorer New Member

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    MPEG compression is a "lossy" data compression method. Algorithms such as Lempel-Ziv-Welch closely examine a data stream looking for ways to perfectly represent the stream using different symbols from the original in order to reduce the volume of data required to reproduce the information. Depending greatly on the actual symbols used to represent the original stream, LZW-based and similar compression utilities can generally be expected to reduce the size of a file by about a factor of two, and the original data stream can be recovered from the new, smaller file perfectly without the loss of a single bit. That is a major reason why zip, arj, gzip, etc. are ubiquitously used to transfer programs and data around the internet. These algorithms could be applied as well to photos, music, and video, but doing so would only reduce a 3 Gbps HD video stream to about 1.5 Gbps. That is not anywhere nearly good enough to make storing and transferring digital music, photos, and video on the internet or over the air, for that matter, practical.

    Fortunately, if we analyze things like photos and video in a different way, there tend to be large areas that are approximately repetitive. In addition, significant amounts of both visual and audible data can be discarded without the human brain being able to tell the difference, or at least not very much or very often. Because of this, we can employ "lossy" compression algorithms to translate the music, photos, or video into much lower bandwidth bitstreams or much smaller files. The recovered output is not at all identical to the original data, but it is close enough for our purposes.

    The question is, "How much data do we throw away?" The answer to that depends on several variables. The first is the nature of the original data. Video (sans the audio) tends to lend itself to greater compression than any other data of which I am aware. Large areas of the screen may be approximately duplicated from one page of video to the next. One relies on the fact the video only changes a little bit from one frame to the next, so the data stream reproduces the picture in full, but then subsequent frames are only represented in the data stream by the changes from the previous page, not the entire page itself. By choosing prudently what we consider enough of a difference how much of a change needs to be represented in the picture at all, we can reduce the data needed to reproduce the next page. Where the line between "prudent" and "imprudent" lies depends upon how much degradation of picture quality we are willing to accept. If one has lower standards, the compression can be greater. As Soapm mentioned, this may depend on the quantity of alcohol one has consumed. :)

    Another variable is the amount of processing power and time available. Analyzing the data more extensively can produce a much tighter bitstream for qualitatively virtually the same results. If one has a monster CPU array with unlimited time, comparatively rather small bitstreams can be created that produce very pleasing results. If one must compress the data in real time with a reasonably economical processor, the stream is going to require rather more bandwidth.

    Of course, the actual content itself has much to do with it. Some video lends itself to greater compression and other video to less without unpleasant artifacts in the output. Other than changing the resolution, the individual doing the authoring doesn't really have much control over the content, but the other factors are much more within his control. That said, most people are gong to want (or absolutely need) to "set it and forget it" when it comes to the compression parameters, and may have rather limited patience in terms of the amount of time required to get things done. (Some compression utilities also have very limited amounts of control offered to the user.) That being the case, rather than recode every movie or at least part of it, observe the PQ, and adjust the compression parameters, one usually just quickly finds a set of compression parameters that almost always produced good results and then sticks with those parameters. That is fine for most of us, but if space is a major concern, one may wish to fiddle with the compression on an individual basis to produce the tightest practical bitstream.

    So yes, 2 hours or even significantly more can fit on a DVD, but one must make compromises in one or more areas to achieve it.
     
  12. Dan203

    Dan203 Super Moderator Staff Member TCF Club

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    Your calculation is a little off. 1920*1088*24*29.97 = 1.5Gbps and that's before chorma sub-sampling* is taken into account. In reality video is transmitted at 4:2:0, which means it's really 1920*1088*12*29.97 = 751Mbps. Throw in your 2:1 compression from LZW and you're down to 375Mbps. Still not practical to transmit, but significantly smaller then 1.5Gbps.

    * Instead of RGB, where each pixel has 8 bits of Red/Green/Blue video uses YUV where the image is separated into one brightness value (luma) and two color values (chroma). In standard broadcast the luma is full resolution, but both of the chroma signals are only 1/4 resolution. So basically each block of 4 pixels is the same color but each individual pixel varies in brightness based on the luma signal.
     
  13. lrhorer

    lrhorer New Member

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    That assumes 1920*1088*24*30. Transmitting 1920*1088*24*60 = 3 Gbps, although of course you are correct about employing YUV coding rather than RGB - but that is just another means of compression. Unless I am much mistaken, 3 Gbps is the maximum bit rate specification for HDMI 1.0. HDMI 2.0 I vaguely seem to recall may even be more. In any case, however, even 100 Mbps would be rather impractical to store and transmit, and it would most definitely have been so when the specs for Blu-Ray and HD QAM were created. In another 5 years, 100Mbps video bitstreams might be very practical, although I suspect unnecessary. 1080p x 60 video is getting to be close to the limit where any visual artifacts (other than compression artifacts, of course) are no longer discernable. Quadrupling the resolution to around 2160p should take the bandwidth of a "perfect" compressed video to about 60 - 80 Mbps, and at that point I don't think further improvement will be of significant value, regardless of picture size. Not, mind you, that I even believe 1080p video will be abandoned for 2160p in the next 5 or even 10 years.
     
  14. Dan203

    Dan203 Super Moderator Staff Member TCF Club

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    No one transmits 1080p@60fps. 1080i@29.97fps is the max for broadcast. Most broadcasters store the "masters" as I frame only MPEG-2 at ~50Mbps with 4:2:2 YUV. I,m sure the production companies save their shows as film, tapes, or lossless digital, but the broadcasters and sindicators have too much stuff and just can't store files that big. One of our biggest business clients is a sindicator and they still get a lot of stuff on tape and have to digitize it themselves. The broadcast sector tends to be pretty far behind technologically compared to even what we can do with our desktop PCs. You'd also be amazed how many times a show is recoded before it hits your TV just to accommodate old equipment. I always get a little chuckle when someone says they don't want to recode to H.264 because they want to preserve the "pristine original". That video has already been recoded like a half dozen, or more, times before it even reaches their DVR.
     
  15. gonzotek

    gonzotek tivo_xml developer

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    Yeah, but why add one more, if you have the space available to store the mpeg2? Recoding to H.264 is still computationally expensive. I do it - for device compatibility reasons, but not on videos I expect to only send back to the tivo. And I treat the resultant output as disposable, keeping the 'original' copy, since that's the best I have access to and it's just easier not to bother. At the rate I personally transfer and store content, disk space/cost simply isn't an issue.
     
  16. Dan203

    Dan203 Super Moderator Staff Member TCF Club

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    Yeah but we get people who complain about the one GOP we have to recode around an edit point. They'll actually do I frame edits just to avoid a dozen frames from being recoded.
     
  17. moyekj

    moyekj Well-Known Member

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    Guilty as charged! I love how easy it is to set cut points on I-Frames in VRD.
     

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