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The Mac mini as a Media Computer

 by Anand Lal Shimpi on February 16, 2005 12:05 AM EST
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39 Comments | Add A Comment
39 Comments

Limitations of iRecord & AV/C Browser

Despite the fact that they work quite well, there are a number of limitations to both of the programs that we looked at from the standpoint of being used as a DVR:
  1. Lack of Guide Functionality - while iRecord is able to record on a schedule, neither iRecord or the AV/C Browser have any knowledge of what's actually airing in your area. For this, you'll have to turn to TV Guide online or TitanTV. There is potential for this sort of functionality to get integrated; however, that would fall on a developer to build up enough interest to do so.
  2. No Preview while Recording – You have to be pretty confident that what you're recording is what you want to be recording because neither of these programs offer a preview of what you're recording. You can view the transport stream as it is being recorded, and Patrick Edson also has a plugin for VLC that lets you watch what's on a channel without actually recording it.
  3. No 5C Encryption Support - Content that has 5C encryption enabled will not be playable, although it will appear to record fine. This will vary from one cable area to the next, but this type of content should primarily be premium channels (e.g. HBO HD). Although, we have seen situations where SD channels also appeared to have 5C encryption enabled.
Other limitations are ones that are surmountable. The data size issue can be worked with as you can always transcode the MPEG-2 transport stream to a smaller format, e.g. DivX. If you are familiar with AppleScript, you can actually build off of the FireWire SDK to add more functionality, which is how many of the initial Virtual D-VHS projects were done.

Performance on the Mac mini

Recording performance is absolutely a non-issue on the mini, since there's no decoding going on. Just simply write the MPEG-2 transport stream to your hard disk. Even when recording the highest bitrate HD streams, we didn't see CPU utilization go higher than 3% on our 1.25GHz Mac mini.

The problem, however, is that we haven't been able to find any applications that offer hardware accelerated MPEG-2 transport stream playback. It seems that the best application for playing back these transport streams natively is VLC (also available for the PC), which doesn't have any sort of hardware decode acceleration support. The end result is that anything above a 13Mbps stream ends up dropping frames on the 1.25GHz Mac mini, meaning that basically all HD streams are unplayable on the mini even though they record fine. The only solution here is to transcode the transport stream to something playable (e.g. DivX) before using your mini as a playback device, which is obviously a lot more work. Another option is to use only the mini as a capture device, and send the transport stream to a fileserver elsewhere in your house for playback or transcoding. The ideal solution would be to have a player that properly took advantage of the hardware, as the 1.25GHz G4 should be enough to playback the MPEG-2 transport stream. Currently, such a solution doesn’t exist for OS X.

Regardless, as impressive as the development support has been around DVR enablement on the mini (and OS X in general), it's still far from complete and far from polished.

The Mac mini as a DVR The Mac mini as a DVD Player
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  • Thresher - Wednesday, February 16, 2005 - link

    This was an excellent read.

    I have a PowerBook and PowerMac G5 and never knew about the Firewire cable box. I am excited about hooking that bad boy up.

  • CrankyTodd - Wednesday, February 16, 2005 - link

    Anand,
    Regarding playback of HDTV Mpeg-2 streams, El Gato's EyeTV software for their EyeTV PVR products is currently far and away the best performer. The software is a free download from their site, and doesnt require you to own one of their PVRs.

    Incidentally, by default it EyeTV won't open certain filetypes... this is an interface issue, not a capability issue. Holding down ctrl-apple while clicking on "Open Quicktime File" in the file menu will allow you to select any file.

  • MIDIman - Wednesday, February 16, 2005 - link

    Superb article.

    "The result is that playing a DVD eats up between 40% - 60% of the 1.25GHz G4 in the Mac mini..."

    This and the visual problems are huge fallbacks as DVD and mp4 playback likely one of the best uses for a mac mini. Granted, not including certain HTPC features (digital audio, CATV in) shows that Apple isn't necessarily orienting this towards such users, but I have a number of friends who plan on purchasing this specifically for this purpose - DVD player, Internet on TV, etc.

    IMHO, this issue alone makes mini-itx desktop-based systems a much more usable alternative. They haven't quite reached the size, but I think they're well within an inch or two.

    Here's a second hand for seeing mp4 codec captures and how the mini handles them, as well as some method of getting in on the nvidia hardware decoding.

  • paulbeers - Wednesday, February 16, 2005 - link

    What about the new Myth TV port for Mac OS X. I know it just came out probably too late for this article, but it is VERY interesting. It doesn't make the Mac Mini an HTPC by itself (the mac mini actually only acts as a front end with a "server" on the network to do all the recording). This actually makes the mac mini even more interesting to me, as per I can build a cheap and basic pc with as many tv cards and storage as I want that could be built from the many parts I have sitting around my house (and be as loud as I want because it isn't in my living room) and have the mac mini in my living room (attractive and quiet) actually playing the content.

    I do agree with Reflex that the lack of digital audio out is a disappointment, and I am riding the fence right now as to whether to buy a Mac Mini or wait for Part Deux as per I am disappointed with the GPU mostly. I would love to hear everyone else's opinions on the matter.

  • Gatak - Wednesday, February 16, 2005 - link

    As for deinterlacing... Well, that shouldn't be a problem if you are connecting to a TV which will render the fields as single frames (as all TVs do, except some new TFT and plasma screens).

    When rendering on the monitor it should be using BOB mode - each field scaled up to a full frame and then rendered at twice the normal framerate (as you have double amount of frames). Even better if there are some smart motion compensation features together with BOB =).

  • AtaStrumf - Wednesday, February 16, 2005 - link

    I'm quite surprised you didn't even try testing how the Mac mini handles different Mpeg 4 video codecs, diffrent audio codecs, different subtitle formats, etc. basicly how it plays "DivXs". With there still not being a perfect set top Divx player I guess I was hoping a MAC mini could serve as one.

    I also missed any mention of how to connect a mini to a SD TV. We have said here under comments, that there is a DVI->S-VIDEO adapter available for MACs, but I think you should make note of it in your article since I'm sure many don't read the comments section or at least not all of them.

    I agree that stereo sound is a bit of a dissapointment, but I don't think all that many people have surround sound in their living rooms to really miss a 5.1 sound output.

  • hopejr - Wednesday, February 16, 2005 - link

    #10, you're forgetting that the first Macintosh, which came out in 1984, was an all-in-one (and I think the Lisa was too).

  • Reflex - Wednesday, February 16, 2005 - link

    First off, they neglected to mention the largest thing that keeps the mini from being an acceptable HTPC: Lack of a digital audio output. If you want to watch your movies in stereo audio, great, but thats only half the experience that DVD offers.

    Put me in the "Cool deal, but I'll wait for v2 crowd". I am interested but its shortcomings are just too much yet even at that price...

    #8: The iMac and iPod were not the first in their class. All-in-One cheap PC's have existed since 94 or so, I know because I owned an old Compaq Presario integrated PC(486 w/14" monitor built in). And MP3 players existed for several years before the iPod. I will say that Apple was the first one to do these things *well* and actually attract media attention to them, but they were not even close to the first in those markets....

  • faboloso112 - Wednesday, February 16, 2005 - link

    great article...keep it up!

  • Zebo - Wednesday, February 16, 2005 - link

    " had phone calls and emails from reporters and other news writers asking me if the mini was a threat to the PC"

    Apple is innovative no doubt about it, but if the Mini works for Apple then dozens of PC clones will come out with thier own PC Minis negating the threat. I kinda feel sorry for Apple sometimes. Always breaching new ground with innovative products only to be copied. IPOD, IMAC are other instances of that.

    Anyway great read as usual from the Master.:)
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