Record eight 1seg stations at once

multiple_tv_mpeg2_stream_capture

[Aaron] tipped us off about a project over at mobilehackerz. They built something of a PVR for 1seg broadcast stations (Google translation). The 1seg broadcast standard is aimed at mobile video service and available in countries like Japan and Brazil. Their terrestrial TV signals (ISDB-T) are divided into 13 segments per channel but the HD broadcasts only use 12 of those segments. This allows the 1seg data to be broadcast in the 13th segment.

mobilehackerz wanted to record each station’s complete daily broadcast. So they picked up a bunch of USB tuner fobs and chained them together with two powered USB hubs. The video is delivered in a type of MPEG2 format so once pulled out of the air the stream can be dumped directly onto disk. It seems they’ve got some code available for this system but even with the translated page we can’t really figure out what it does. If you’re Japanese skills are strong, fill us in with a comment.

At 3000 yen (about $34) per tuner this is not the most economical PVR capture system we’ve seen. Add to that the 15 fps broadcast and we’re not sure this is of all that much use. But then again, if you have to ask “what is it for?” you’re missing the essence of the hack.

Comments

  1. David Ruger says:

    If you would like a translation, I can help you, but it won’t be cheap

  2. rasz says:

    gotta love ghetto antenna daisy chain

  3. Rounin says:

    Ohh.. Come on, help the community.

    Any way here is my translation:

    perlRTMP

    RTMP server written in perl.

    Formats

    * MPEG2-TS (.ts) MPEG2-TS (. Ts)
    * MP4 (.mp4) MP4 (. Mp4)
    * “24hour1segGuy”(.ts & .idx)

    Why perl?

    It was the only language I could use freely.
    If similar things can be written in ruby why not in perl.

    Why MPEG2-TS?

    Intrigued by “24hour1segGuy” I made a 24 hour 1seg recording server, for Linux.
    To watch via streaming (or progressive download) from a Windows box it ends up having to be converted to MP4, and that takes time.
    And when converting to MP4, some VFR stations will end up with video/audio syncing problems, and trying to prevent that by extrapolating time and re-embedding to sync takes too much time again.
    A stream which transmits video and audio simultaneously will not have that problem, so I was left thinking it would be nice to have a RTMP server that could handle MPEG2-TS directly.

    Sister sites

    * OneSeg24 for Linux
    * http://code.google.com/p/oneseg24/

    Reference

    * RubyIZUMI
    * http://code.google.com/p/rubyizumi/

    * “24hour1segGuy”
    * http://mobilehackerz.jp/contents/OneSeg24

    * [UOT-100]24hour1segGuy Part03[LOG-J200]
    * http://pc11.2ch.net/test/read.cgi/avi/1232374302/

  4. mad_max says:

    David Ruger: “If you would like me to extort money from you, I can, but it won’t be cheap.”
    Props for trying.

  5. Doc Oct says:

    Neat hack, too bad we can’t use it in the states. :(

    I wonder how much storage that takes up? I guess 1seg isn’t that much to begin with but how much hdd space can that take if he’s recording a bunch (8?) 24hrs a day?

  6. rasz says:

    one stream is ~45KB/s max, so 1.2GB an hour, 30GB a day. 1TB drive holds one month.

  7. Doc Oct says:

    You sure? If it is 45KB/s max then that should only be 162MB/hr, 3.9GB/day, 116GB/month. That isn’t too bad I guess.

  8. mojo says:

    1seg is fairly low bandwidth and is designed for reception on mobile devices like phones. The version in use in Japan is IIRC 320×240 at about 400Kb/sec. The Japanese version runs at 15fps while the Brazilian one uses 30fps which results in blockier images but smoother motion.

    IIRC the law in Japan is that the 1seg channel has to carry the same content at the HD channel it shares with.

  9. tw says:

    @Doc Oct 45KB/s per stream, 1.24GB/h for 8 streams.

  10. Frogz says:

    isnt it obvious?
    use it to capture all channels and re-broadcast to the net to a free or pay service(sell it to americans who are obsessed with japan)

  11. cantido says:

    @Rounin

    What a dry translation.. e.g;

    >If similar things can be written
    >in ruby why not in perl.

    >rubyで出来るならperlでも出来るんじゃないか、と。

    [If Ruby can do it, even Perl can do it right?]

    Sounds like he’s shitting Ruby to me, you wouldn’t get that from your translation though.

  12. cantido says:

    @Frogz

    Most of the stuff you could watch on OneSeg is up on youtube or ニコニコ anyways… some evenings you can catch some crappy american action film dubbed by what sounds like drunken salary men though, which is good for a laugh.

  13. YenTheFirst says:

    Here’s some additional thoughts on the translation.
    I’ll have to go through and translate the full article, too. :)

    @Rounin did a pretty good job.

    “Formats” is really “Supported Formats”
    I think『24時間ワンセグ野郎』 is the name of the actual project, so I’m not sure if it should be translated or not. “24-hour 1seg Guy” sounds good enough to me. I think in this case, though “24-hour 1seg bastard” might be closer.
    「野郎」 is kinda derogatory, and the project does look kinda hackey that way, it’s just a bunch of receivers in hubs.

    “It was the only language I could use freely.”
    I’m not positive about this translation, but I have no idea. how did you translate 「くらいしかなかった」 ?

    the second line, I’d write as
    ” I was thinking, “If it can be done in ruby, then why can’t it be done in perl?” ”

    I don’t think this is about shitting on ruby, I think it’s because the author used RubyIZUMI as a reference for this project, and the two languages are similar enough that porting code shouldn’t be hard.

    finally,
    “Intrigued by “24hour1segGuy” I made a 24 hour 1seg recording server, for Linux.”
    It might be ‘inspired by’, ‘for’ or ‘starting off from’. not sure. But the “for linux” part is a separate sentence , and I think this is intentional.
    maybe: “Inspired by “24hour1SegGuy”, I made a 24 hour 1seg recording server. But for Linux.”

  14. PSN Coder says:

    This isn’t half bad, I could see it going somewhere.

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