DTMB capture

Task

Can you help Red Hen develop the systems needed to capture DTMB television broadcasts?
If so, write to

and we will connect you with a mentor.

Related links

DTMB

DTMB is a major standard for digital broadcast.  It is used in China, Hong Kong, and Cuba and may be adopted in other nations. 
The GB20600-2006 standard described may just specify the transport stream format and not the digital layer, which is what we can process in software.

For information on DTMB hardware, see
A new initiative is the Joker TV device and drivers, see linux-kernel message, with support for DTMB and several other standards.

Linux support

DVEO provides a Linux SDK for their 
TVB593 DTMB capture card; for Red Hen Lab, a LAN-based tuner like HDHomeRun or a USB tuner would be preferable to a PCIe capture card.

Linux driver development
  1. CTTB driver patch (linux-media 2011, Mauro Carvalho Chehab)
  2. DTMB support for DVB API (linux-media 2012, Antti Palosaari)
  3. Better document DTMB time interleaving (linuxtv 2015, Mauro Carvalho Chehab)
  4. Joker TV (2017) -- github
  5. Submit bug reports for DTMB to linux-media@vger.kernel.org -- subscribe and archive
Linux Kernel developer Antti Palosaari <crope@iki.fi> has written some basic DTMB support into the Linux kernel, see blog entry. He also wrote a HDIC HD29L2 DTMB (aka CMMB or DMB-T/H) demodulator driver (hd29l2) for kernel 3.3, but notes there is no longer any public hardware for that driver.

For discussion (in Chinese) of Linux in Hong Kong and China, see
  1. HKEPC Forum (Hong Kong)

Android support

Several devices appear to be supported in Android:

Text extraction

CCextractor probably does not yet handle DTMB text extraction -- we don't have any samples yet to test.

The HKCA1108.pdf regulatory document from the Hong Kong government states that "Receivers shall include provisions to decode and display subtitles conforming to ETSI EN 300 743." This is the specification that regulates European subtitles over DVB. It's possible that DTMB regulates only the physical signal but has nothing to do with subtitles or video encoding.

Similarly this Test Procedure document from the Cuban government says "The TV Set is intended for the reception of DTMB Digital Terrestrial Television in 6MHz bandwidth, according to the specifications GB 20600-2006 and DVB subtitles (ETSI EN 300 743). The DUT must support DVB subtitles (ETSI EN 300 743)."

Next Steps

  1. Get some recordings of broadcast streams—not examples from the web, which do not include digital closed captions.
  2. Get the technical specifications documents on the DTMB standard that would be needed by CCextractor staff to add support for DTMB.