Building Digital TV support on Linux - Linux Foundation

Aug 21, 2014

© 2014 SAMSUNG Electronics Co.

Not to be used for commercial purpose without getting permissionAll information, opinions and ideas herein are exclusively the author's own opinionOpen Source Group – Silicon Valley

Samsung Research Brazil

Building Digital TV support on Linux

Mauro Carvalho ChehabLinux Kernel Expert

Samsung Open Source Group

© 2014 SAMSUNG Electronics Co.Open Source Group – Silicon ValleySamsung Research Brazil

Biography● Maintainer of the media and EDAC subystems at the Linux

Kernel

● Works at Samsung Research Brazil as R&D Director on Open Source, being part of the Samsung's Open Source Group.

● Worked during 5 years at Red Hat, where, besides maintaining the upstream Kernel subsystems, were also responsible for maintaining several subsystems at RHEL's Kernel;

● Developed several device drivers for video stream capture and analog/digital TV reception at the Linux Kernel, including most of the drivers for the Brazilian digital TV standard (SBTVD / ISDB-T).


Digital TV challenges● Major standards:

– ATSC - Advanced Television System Committee● Defined in United States

– DVB - Digital Video Broadcasting● Defined in Europe

– ISDB – Integrated Services Digital Broadcasting Terrestrial

● Defined in Japan– DTMB - Digital Terrestrial Multimedia Broadcast

● Defined in China


Digital TV challenges● Digital TV variants:

– Terrestrial (air) standards are used by air broadcasts: ATSC, DVB-T, DVB-T2, ISDB-T, DMB;

– Cable standards are used by cable operators: DVB-C, DVB-C2, ClearQAM (DVB-C Annex B), ISDB-C;

– Satellite standards are used by Satellite operators: DVB-S, DVB-S2, ISDB-S.


Digital TV Terrestrial Standards

Source: http://en.wikipedia.org/wiki/File:Digital_broadcast_standards.svg

Updated in November, 2013Note: DVB-T2 is gradually replacing DVB-T

http://en.wikipedia.org/wiki/File:Digital_broadcast_standards.svg


8 Mhz

TV Digital standards

Video Elem. Stream

Audio Elem. Stream

Modulation

Transport

Channel1.7 Mhz 5 Mhz 6 Mhz 7 Mhz 10 Mhz

VSB COFDM COFDM-BSTQAM QPSK

MPEG2 – Transport Stream

MPEG2 MPEG4

280i LD 480iSDTV 720pEDTV 1080iHDTV

MPEG2-BC MPEG2-AAC

DOLBYAC3

MPEG4-AAC

Copyright © 2006-2014 Mauro Carvalho Chehab – GPLv2 licensed


8 Mhz

TV Digital Linux Mapping

Video Elem. Stream

Audio Elem. Stream

Modulation

Transport

Channel1.7 Mhz 5 Mhz 6 Mhz 7 Mhz 10 Mhz

VSB COFDM COFDM-BSTQAM QPSK

MPEG2 – Transport Stream

MPEG2 MPEG4

280i LD 480iSDTV 720pEDTV 1080iHDTV

MPEG2-BC MPEG2-AAC

DOLBYAC3

MPEG4-AAC

Copyright © 2006-2014 Mauro Carvalho Chehab – GPLv2 licensed

Kernelspace

Userspace


Media device block diagram

TunerFM/TV

Audio decoder

Video decoder

Audio encoder

Button Key/IR input logic

EEPROM

Sensor

Bridge to CPU/Chipset bus

I2C

Bus

Sys

tem

Bus

Frontend

SEC

Transport Stream filter

Conditional Access Module

Video encoder

Radio / Analog TV

Digital TV

PS.: picture is not complete: other blocks may be present,Like audio/video A/D and D/A, HDMI decoder/encoder, etc.

Webcam

PCI,USB,PCIe,...Processing blocks

Smartcard


●Video4Linux API (version 2)

TunerFM/TV

Audio decoder

Video decoder

Audio encoder

Sensor

Video encoder

Radio / Analog TV

Webcam

● For webcams, video inputs/outputs and radio, video and analog TV

● Extensions for Software Digital Radio added (Drivers in staging as API might change)

● Audio output uses the standard ALSA API


●Remote Controller / Input APIs

Button Key/IR input logic

● Used for Remote Controllers and Webcam buttons● It is an extension of the standard Linux Input API (evdev)


Linux Kernel DTV APIs

● Despite being called Linux DVB API, it covers all standards

● Each frontend, CA and Demux device on a DTV card is exported

● The frontend control is complex, as it is standard-dependent and Country dependent;

● Satellite Equipment Control (SEC) setup is also complex:

– Contorls LNBf and smart devices (DiSEqC);

Frontend

SEC



Digital TV

DVB Frontend API

DVB CA API

DVB Demux API Smartcard

Frontend

SEC



Digital TV

DVB Frontend API

DVB CA API

DVB Demux API


Media Controller API

● To control complex devices with configurable pipelines

● Currently, used only on embedded devices and on UVC (USB Video Class)

● Subdev API

– To control each single logical element on such complex devices

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Summary of Media Kernel APIs● APIs described at: http://linuxtv.org/downloads/v4l-dvb-apis/

– Video4Linux API (version 2)● For webcams, video inputs/outputs and radio, video and analog

TV– Linux DVB API (version 5)

● For digital TV inputs– Remote Controller / Input evdev APIs

● For Remote Controllers– Media Controller and Subdev APIs

● To control complex devices with configurable pipelines● The Advanced Linux Sound Architecture (ALSA)

– For audio inputs, outputs, mixers (and sequencers)● Standard input evdev API

– For webcam/grabber buttons and remote controllers

http://linuxtv.org/downloads/v4l-dvb-apis/

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DVB API history● DVBv1: the old Nokia API (1998-1999?)

– Developed/Implemented for a Nokia project developed by Convergence

● DVBv2: major re-factoring step (2000-2002?)

– Stabilized the API for DVB-T/C/S; ATSC

● DVBv3: namespace cleanups

– First version on Kernel – Jun/2003 – for Kernel v2.5.74

● DVBv4: An abandoned WIP project (2004-2005)

– Meant to add all features for STB, but never finished.

● DVBv5: Current version

– Committed in Kernel 2.6.28 (2008).

– Added full multi-standard support. Frontend-only changes.

– New standards generally support DVBv3 legacy calls, with drawbacks

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CHANNELTRANSPONDER

MPEG TS example

MPEG TS

Service 1

Video

Audio 1

Audio 2

Service 2

Video

Audio 1

Audio 2

PID 100

PID 101

PID 102

PID 200

PID 231

PID 554

Virtual Channel 17.1

Virtual Channel 17.2

Other PIDs


Userspace library: libdvbv5● Abstracts the difference between DVBv3 and DVBv5;

● Written from scratch to fully support DVBv5;

● Provide a standard way to work with all DVB standards;

● Offers functions to discover the TV streams (“channels”) that are present inside a transport stream;

● Offers functions to read/write both legacy data formats used by DVBv3 applications and to read/write data compatible with DVBv5.

● It is new: the API just stabilized in April, 2014.

– Currently, used by DVBv5 utils and by some other tools;

– New projects should start using it.


DVBv5 utils and libdvbv5● DVBv5 utils:

– Uses the libdvbv5 as basis for scan/zap and read/write channel files;

– It consists of 4 tools:

● Both DVBv5 utils and libdvbv5 are packaged together with v4l-utils:

– http://git.linuxtv.org/cgit.cgi/v4l-utils.git/

● The dynamic library is released on v4l-utils version 1.2 (Jun, 28 2014)

dvbv5-scan Scans the channel transponders and gets the services available there

dvbv5-zap Locks into a channel (zap), allowing other applications to get the stream at the dvr devices or to monitor the stream

dvb-fe-tool Lists frontend properties and allow to manually set the DVB frontend

dvb-format-convert Converts from/to several other formats used by DVBv3 apps

http://git.linuxtv.org/cgit.cgi/v4l-utils.git/


GUI apps using libdvbv5● Kaffeine has a recent experimental addition of libdvbv5 support:

– It is a KDE media player with support for several types of input, including Digital TV (ATSC, DVB-S, DVB-S2 and DVB-C);

– The experimental patches also adds support for ISDB-T;

– Should not be hard to add support for DVB-T2 and other modern standards;

– Need more testing and bug fixes;

– Located at: http://git.linuxtv.org/cgit.cgi/mchehab/kaffeine.git/● Tvdaemon:

– It is a TV streaming server;

– It is a fork/rewrite of tvheadend;

– Located at: https://github.com/neolynx/tvdaemon

http://git.linuxtv.org/cgit.cgi/mchehab/kaffeine.git/

https://github.com/neolynx/tvdaemon


DVB-C Scan Example$ dvbv5-scan ~/dvbc-teste -I channel

Scanning frequency #1 573000000

Lock (0x1f) Quality= Good Signal= 100.00% C/N= -13.80dB UCB= 0 postBER= 3.14x10^-3 PER= 0

Service SBT, provider (null): digital television

Service Globo, provider Globo: digital television

Service Record, provider (null): digital television

Service Band, provider (null): digital television

...

Service Trilhas Sonoras, provider (null): digital radio

New transponder/channel found: #2: 579000000

...

New transponder/channel found: #39: 507000000


Service zap example$ dvbv5-zap -c dvb_channel.conf "trilhas sonoras" -r

using demux '/dev/dvb/adapter0/demux0'

reading channels from file 'dvb_channel.conf'

service has pid type 05: 204

tuning to 573000000 Hz

audio pid 104

dvb_set_pesfilter 104


DVR interface '/dev/dvb/adapter0/dvr0' can now be opened


DVB DVR device play$ mplayer -cache 800 /dev/dvb/adapter0/dvr0

MPlayer SVN-r37077-4.8.2 (C) 2000-2014 MPlayer Team

TS file format detected.

NO VIDEO! AUDIO MPA(pid=104) NO SUBS (yet)! PROGRAM N. 0

==================================================================

Opening audio decoder: [mpg123] MPEG 1.0/2.0/2.5 layers I, II, III

AUDIO: 48000 Hz, 2 ch, s16le, 192.0 kbit/12.50% (ratio: 24000->192000)

Selected audio codec: [mpg123] afm: mpg123 (MPEG 1.0/2.0/2.5 layers I, II, III)

==================================================================

AO: [alsa] 48000Hz 2ch s16le (2 bytes per sample)

Video: no video

Starting playback...


DVB transponder traffic monitor$ dvbv5-zap -c dvb_channel.conf 573000000 -m

using demux '/dev/dvb/adapter0/demux0'

reading channels from file 'dvb_channel.conf'

service has pid type 05: 204

tuning to 573000000 Hz


dvb_set_pesfilter to 0x2000

PID FREQ SPEED TOTAL

0000 9.88 p/s 14.5 Kbps 1 KB

0001 1.98 p/s 2.9 Kbps 376 B

0010 18.77 p/s 27.6 Kbps 3 KB

0011 48.42 p/s 71.1 Kbps 8 KB

0012 1455.53 p/s 2137.8 Kbps 270 KB

...

1fff 1033.60 p/s 1518.1 Kbps 192 KB

TOT 25296.44 p/s 37154.2 Kbps 4700 KB


How to contribute● Main discussions and patches related to both Kernel drivers and

libdvbv5 happen via mailing lists:

– [email protected]

● How to get and test the latest drivers:

– See http://git.linuxtv.org/media_build.git

● Upstream development tree:

– http://git.linuxtv.org/media_tree.git

● DVBv5 tools and libdvbv5:

– http://git.linuxtv.org/v4l-utils.git

● Wiki pages: http://linuxtv.org/wiki/

● IRC channel: irc.freenode.net

– channels #v4l and #linuxtv

– Can be assessed via http://webchat.freenode.net/

mailto:[email protected]

http://git.linuxtv.org/media_build.git

http://git.linuxtv.org/media_tree.git

http://git.linuxtv.org/v4l-utils.git

http://linuxtv.org/wiki/

http://webchat.freenode.net/

24

Thank you.


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Building Digital TV support on Linux - Linux Foundation