ISDB caption support
What is the status of ISDB-Tb / ISDB-T International / ISDB Japanese closed captioning support?
If anyone is working on this, please get in touch -- we're particularly interested in getting Brazilian SBTVD working.
I see Mauro has been working on DVBv5 support, but does this include captioning?
Cheers,
David
Hi David,
ISDB-T subtitles are done in a similar manner to DVB-T subtitles - there is a PID in the stream which contains the subtitle data, which needs to be decoded by the application (just as you would handle DVB-T subtitles or ATSC closed captions). It's entirely an application level function, having nothing to do with the driver layer.
In short, this has nothing to do with DVBv5, as that is all about how the tuner is controlled, not what gets done with the resulting MPEG stream. You would need to talk to whoever is responsible for the application you are working with (whether that be VLC, mplayer, ccextractor, etc).
Cheers,
Devin
Quoted 16 lines · David Liontooth
What is the status of ISDB-Tb / ISDB-T International / ISDB Japanese closed captioning support?
If anyone is working on this, please get in touch -- we're particularly interested in getting Brazilian SBTVD working.
I see Mauro has been working on DVBv5 support, but does this include captioning?
Cheers,
David
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Signature · 2 lines
Devin J. Heitmueller - Kernel Labs http://www.kernellabs.com
Hi Devin,
Great, thanks.
I realize captions is an application-layer function, and intend to work with the CCExtractor team. Do any other applications already have ISDB caption support?
For DVB and ATSC there's quite a bit of code written by several people for teletext and captions -- has anything at all been done for ISDB captions?
It's used in nearly all of Central and South America, plus the Philippines and of course Japan -- you would have thought someone has started on the task?
We're looking for a good solution for capturing television in Brazil, when the signal is encrypted -- are there set-top boxes or tv capture cards that handle the decryption so that the decoded signal is passed on with the ISDB-Tb caption stream intact?
Our test system generates captions as an overlay and does not pass on the closed captions.
Cheers,
David
Quoted 36 lines · Devin Heitmueller
Hi David,
ISDB-T subtitles are done in a similar manner to DVB-T subtitles - there is a PID in the stream which contains the subtitle data, which needs to be decoded by the application (just as you would handle DVB-T subtitles or ATSC closed captions). It's entirely an application level function, having nothing to do with the driver layer.
In short, this has nothing to do with DVBv5, as that is all about how the tuner is controlled, not what gets done with the resulting MPEG stream. You would need to talk to whoever is responsible for the application you are working with (whether that be VLC, mplayer, ccextractor, etc).
Cheers,
Devin
Quoted 15 lines · David Liontooth
What is the status of ISDB-Tb / ISDB-T International / ISDB Japanese closed captioning support?
If anyone is working on this, please get in touch -- we're particularly interested in getting Brazilian SBTVD working.
I see Mauro has been working on DVBv5 support, but does this include captioning?
Cheers,
David
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Quoted 3 lines
I realize captions is an application-layer function, and intend to work with the CCExtractor team. Do any other applications already have ISDB caption support?
Based on a Google search, it looks like dvbviewer can decode them:
http://www.dvbviewer.tv/forum/topic/41933-brazilian-terrestrial-isdb-tb-subtitles-closed-caption/
http://www.dvbviewer.com/en/index.php
It's not open source, and it's not Linux, but at least it may give you something to compare against if you want to build the functionality yourself.
Quoted 2 lines
For DVB and ATSC there's quite a bit of code written by several people for teletext and captions -- has anything at all been done for ISDB captions?
Not to my knowledge. I've done a ton of work with CC decoding in VLC, but haven't poked around at the other formats.
Quoted 5 lines
It's used in nearly all of Central and South America, plus the Philippines and of course Japan -- you would have thought someone has started on the task?
From what I understand, most terrestrial TV in Japan is encrypted, so
you're likely to not find many open source solutions which targeted at that market. Presumably there is less of that in Brazil (why else would Mauro be doing all that ISDB-T work if there was no way to watch the actual video?).
Quoted 4 lines
We're looking for a good solution for capturing television in Brazil, when the signal is encrypted -- are there set-top boxes or tv capture cards that handle the decryption so that the decoded signal is passed on with the ISDB-Tb caption stream intact?
This would be very unusual. Satellite captioning often has the same issues - the decoders only support overlaying the captions over the video and provide no means to access the underlying data.
Devin
Signature · 2 lines
Devin J. Heitmueller - Kernel Labs http://www.kernellabs.com
Em Fri, 28 Nov 2014 22:23:13 -0500
Devin Heitmueller <[email protected]> escreveu:
Quoted 3 lines
Quoted 3 lines
I realize captions is an application-layer function, and intend to work with the CCExtractor team. Do any other applications already have ISDB caption support?
I never actually checked how CC works on ISDB-T. On the MPEG-TS tables I worked so far, ISDB-T is very close to DVB, so I would expect that CC would also be close to the DVB descriptors for it, but, as I said, I never actually read that part of the ARIB/ABNT specs.
Quoted 19 lines
Based on a Google search, it looks like dvbviewer can decode them:
http://www.dvbviewer.tv/forum/topic/41933-brazilian-terrestrial-isdb-tb-subtitles-closed-caption/
http://www.dvbviewer.com/en/index.phpIt's not open source, and it's not Linux, but at least it may give you something to compare against if you want to build the functionality yourself.
Quoted 2 lines
For DVB and ATSC there's quite a bit of code written by several people for teletext and captions -- has anything at all been done for ISDB captions?
Not to my knowledge. I've done a ton of work with CC decoding in VLC, but haven't poked around at the other formats.
Quoted 3 lines
It's used in nearly all of Central and South America, plus the Philippines and of course Japan -- you would have thought someone has started on the task?
Quoted 10 lines
From what I understand, most terrestrial TV in Japan is encrypted, so you're likely to not find many open source solutions which targeted at that market. Presumably there is less of that in Brazil (why else would Mauro be doing all that ISDB-T work if there was no way to watch the actual video?).
Quoted 4 lines
We're looking for a good solution for capturing television in Brazil, when the signal is encrypted -- are there set-top boxes or tv capture cards that handle the decryption so that the decoded signal is passed on with the ISDB-Tb caption stream intact?
I'm not aware of any device that handles encryption in Brazil. Cryptography is used only in Japan standard, as far as I know.
All channels here are in clear, at least for video/audio streams, but, as I said, I never tried to work with CC for ISDB-T. Yet, I would find really weird if just CC is encrypted.
Quoted 7 lines
This would be very unusual. Satellite captioning often has the same issues - the decoders only support overlaying the captions over the video and provide no means to access the underlying data.
Devin
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HI David,
Em Sat, 29 Nov 2014 08:17:30 -0800
David Liontooth <[email protected]> escreveu:
Quoted 10 lines
Hi Mauro,
Thank you; that's extremely helpful. We are looking into how much work it will be to write an ISDB-Tb captioning decoder for CCExtractor.
Can we find a list of television capture hardware devices known to work in Brazil? Our friends in Rio are new to all this, and
linux/Documentation/dvb# grep -i ISDB *
finds nothing. I'm aware of Linux TV's list of ISDB resources, but they don't specify ISDB subtype (ISDB-Tb) -- are they interchangeable?
Yes, the demod here is the same as the ones used in Japan. The only difference is that the devices sold in Japan has the additional crypto modules.
There are drivers that supports ISDB-T:
$ git grep -l SYS_ISDBT|grep -v tuners Documentation/DocBook/media/dvb/dvbproperty.xml drivers/media/common/siano/smsdvb-main.c drivers/media/dvb-core/dvb_frontend.c drivers/media/dvb-frontends/dib0070.c drivers/media/dvb-frontends/dib0090.c drivers/media/dvb-frontends/dib8000.c drivers/media/dvb-frontends/mb86a20s.c drivers/media/dvb-frontends/s921.c drivers/media/dvb-frontends/tc90522.c drivers/media/pci/pt1/va1j5jf8007t.c drivers/media/pci/pt3/pt3.c drivers/media/usb/dvb-usb/friio-fe.c include/uapi/linux/dvb/frontend.h
I never found any PT1 or PT3 devices here. The friio is also sold only in Japan, afaikt. The devices based on s921 are really crap (and only 1seg).
So, basically the devices supported are based on either one of those demods:
Dibcom 80xx Toshiba mb86a20s Siano Rio
I suspect that the easier ones to find nowadays are the PixelView ones that are based on cx231xx/mb86a20s:
PixelView PlayTV USB 2.0 SBTVD Full-Seg - PV-D231U(RN)-F
Not the best ISDB-T chip, but it works if they have a good antenna. There are other devices too, but the brand names change a lot, and, as I didn't buy or received any new isdb-t devices those days, I'm unsure what other devices have inside.
If your friends want, they could ping me back and I can try to help them to find some devices.
With regards to CC decoding, IMHO, the best would be to add a parser for ISDB CC at libdvbv5.
Regards,
Quoted 2 lines
With regards to CC decoding, IMHO, the best would be to add a parser for ISDB CC at libdvbv5.
It probably makes more sense to extend one of the existing libraries that supports captions/subtitles to include support for ISDB (such as libzvbi or ccextractor). The libdvbv5 library has no infrastructure today for subtitle rendering for any other formats, so generating a generic caption/subtitle API within libdvbv5 that is extensible enough to support other formats seems redundant. It also means that applications that already use libzvbi will get the support for ISDB effectively "for free" (in fact, I'm considering moving VLC over to using libzvbi for CC rendering - it's already used today for raw VBI slicing).
Devin
Signature · 2 lines
Devin J. Heitmueller - Kernel Labs http://www.kernellabs.com
Quoted 3 lines
I realize captions is an application-layer function, and intend to work with the CCExtractor team. Do any other applications already have ISDB caption support?
there's a mplayer patch for subtitle support:
https://github.com/0p1pp1/mplayer/commit/6debc831d34cad98d1b251920fbdb48f74a880df
It translates subtitle stream PES to ASS, but is is for ISDB-T/Japan. Subtitling in ISDB-T depends heavily on the control sequences of the original character encoding (ARIB STD-B24),
so I'm afraid that (at least) PES format is very different in ISDB-Tb.
regards,
akihiro