Digital TV on Linux -...

Oct 14, 2014

© 2014 SAMSUNG Electronics Co.

Not to be used for commercial purpose without getting permissionAll information herein are my own and may not represent the company's positions, strategies or opinionsOpen Source Group – Silicon Valley

Samsung Research Brazil

Digital TV on Linux

Mauro Carvalho ChehabLinux Kernel Expert

Samsung Open Source Group

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

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 May, 2014Note: DVB-T2 is gradually replacing DVB-T

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

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

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


TV Digital standards

Copyright © 2006-2014 Mauro Carvalho Chehab – GPLv2 licensed

8 Mhz

Video Elem. Stream

Audio Elem. Stream

Modulation

Transport

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

VSB QAM

MPEG2 MPEG4

280i LD 480iSDTV 720pEDTV 1080iHDTV

MPEG2-BC MPEG2-AAC

DOLBYAC3

MPEG4-AAC

QPSK COFDM COFDM-BST TDS-OFDM

MPEG2 – Transport Stream


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 QAM

MPEG2 MPEG4

280i LD 480iSDTV 720pEDTV 1080iHDTV

MPEG2-BC MPEG2-AAC

DOLBYAC3

MPEG4-AAC

Copyright © 2006-2014 Mauro Carvalho Chehab – GPLv2 licensed

Kernelspace

Userspace

QPSK COFDM COFDM-BST TDS-OFDM

MPEG2 – Transport Stream


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 were added recently

● 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:

– Controls 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: controls each logical element on complex devices


Media controller API● Discovering a device internal topology

– hardware devices are modeled as an oriented graph

– building blocks called entities connected through pads.

● An entity is a media hardware or software building block

– correspond to logical blocks: physical/logical hardware devices, DMA channels, physical connectors

● A pad is a connection endpoint

– Represents interactions between entities

– Data flows from the entity's output to one or more entity inputs

● A link is a point-to-point oriented connection between two pads

– Data flows from source to sink pads


Sub-devices● sub-devices are usually kernel-only objects

– If a driver implements the media device API:● Applications will be able to:

– enumerate the sub-devices– discover the hardware topology

● In addition to make sub-devices discoverable:

– drivers can also choose to make sub-devices directly configurable

● sub-devices will feature a character device node

– on which ioctls can be called to affecting directly that subdevice

– image formats can be negotiated on individual pads● Currently, only available for V4L2

● Adding support for DVB will require more work

14


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/

15


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

16


PHYSICALCHANNEL /

TRANSPONDER

MPEG-TS container example

MPEGTransport

Streamcontainer

Program 1(service ID 1000)

Video

Audio 1

Audio 2

Program 2(service ID 2000)

Video

Audio 1

Data

PID 100

PID 101

PID 102

PID 200

PID 231

PID 554

Virtual Channel 17.1: playing movie (HD)

Virtual Channel 17.2: playing news (SD)

Other PIDs

NOTE:The PID and Service ID

data are described on sometables inside the MPEG-TS:

PAT/PMT plus:SDT(DVB, ISDB) orTVCT/CVCT (ATSC)


Kernel system calls used on media● The media API devices are accessed via Kernel system

calls:

– open() - opens a device node for read or read/write access;

– close() - closes a device node, releasing resources;

– ioctl() - sends/receives special commands to the device;

– read() - reads some data from an input device;

– write() - sends some data to an output device;

– poll() - checks if something is a available for input, if output finished or if an I/O error (or event) occurred;

– mmap() - creates a shared memory to be used by both the application and the device (currently, only V4L2).


DVBv3 APIstruct dvb_qpsk_parameters { /* DVB-S */

__u32 symbol_rate;fe_code_rate_t fec_inner;

};

struct dvb_qam_parameters { /* DVB-C */__u32 symbol_rate;fe_code_rate_t fec_inner;fe_modulation_t modulation;

};

struct dvb_vsb_parameters { /* ATSC */fe_modulation_t modulation;

};

struct dvb_ofdm_parameters { /* DVB-T */fe_bandwidth_t bandwidth;fe_code_rate_t code_rate_HP;fe_code_rate_t code_rate_LP;fe_modulation_t constellation;fe_transmit_mode_t transmission_mode;fe_guard_interval_t guard_interval;fe_hierarchy_t hierarchy_information;

};

struct dvb_frontend_parameters {__u32 frequency;fe_spectral_inversion_t inversion;

union { struct dvb_qpsk_parameters qpsk; struct dvb_qam_parameters qam; struct dvb_ofdm_parameters ofdm; struct dvb_vsb_parameters vsb;

} u;};


Digital TV frontend properties● The Linux DVB frontend API sets/gets the frontend properties.

● At Linux DVB API version 5, it is based mainly on two ioctl() syscalls:

– FE_GET_PROPERTY: This ioctl call returns one or more frontend properties.

● Only requires read-only access to the device to read the props from a cache.

– FE_SET_PROPERTY: This ioctl call sets one or more frontend properties.

● Read/write access is required to write the props at the kernel cache.

– Each property consists of a key and its associated value.

– Several properties can be get/set at the same time.● NOTE: other ioctls also defined at DVBv3 are still used, like:

– FE_READ_STATUS – reads frontend lock status


DVBv5 properties example● For example, to receive a DVB/C channel at 651 kHz, the

following properties should be filled with:

– FREQUENCY = 651000000

– MODULATION = QAM_256

– INVERSION = INVERSION_AUTO

– SYMBOL_RATE = 5217000

– INNER_FEC = FEC_3_4

(inner convolutional code FEC = 3/4)– DVB_TUNE = <any value>

● This special property writes data from the previous properties stored at the cache into the hardware


Digital TV demux settings● The DVB demux API provides ways to filter the MPEG TS and read

its contents

● The most used ioctl syscals are the ones that set the filters:

– DMX_SET_BUFFER_SIZE – Sets the size of the circular buffer used to store the filtered data

– DMX_SET_FILTER - This ioctl call sets up a MPEG-TS packet filter according to the filter and mask parameters provided (up to the 16 bytes of the packet can be filtered).

– DMX_SET_PES_FILTER - This ioctl call sets up a Program Elementary Stream (PES) filter according to the parameters provided. It filters just the packet identifier (PID)

● A PID equal to 0x2000 means to just send the entire MPEG-TS as-is to userspace. Generally, only used for testing purposes, especially on embedded or USB-based devices, as this eats a lot of CPU time and bus bandwidth.

● Once a filter is set, the data is read via the dvr device node, using poll() and read() syscalls.


Userspace library: libdvbv5● Written from scratch to fully support DVBv5;

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

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

● Offers functions to read/write files on both legacyformats used by DVBv3 applications and to read/write data compatible with DVBv5.

● Used by DVBv5 utils, tvdaemon, Kaffeine (at linuxtv.org);

● The API stabilized in April, 2014.

– Released at v4l-utils version 1.4.0 (Sept, 8 2014)

– Fully documented at v4l-utils version 1.6.0 (Oct, 5 2014)

– Already packaged for Fedora and Debian (a Tizen package is also available at linuxtv.org – pending to be pushed upstream)

– New projects should start using it.


The libdvbv5 library● The Library uses internally (key, value) sets, just like the DVBv5 API

– All DVBv5 sets are supported

– Additional properties for Satellite Equipment Control(SEC) config

– Additional properties for derived statistics;● The logic to configure SEC should be in userspace, as only the

application knows:

– Satellite LNBf, with converts from C-Band/Ku-Band/... into S-Band, used by the satellite TV devices;

– Parameters to select the satellite dish/LNBf, to change the dish position and to select the LNBf frequency range/polarization.

● As the DVB evolved, there are different ways to do the same thing, e. g. via the latest DVBv5 API spec or to use some fallback code when running a DVBv5 API lower than version 5.10 or even DVBv3.


The libdvbv5 features summary● It abstracts the DVB version, supporting all types of drivers

from version 3.2 and up;

● It allows setting parameters related to the satellite system;

● It provides a way to receive the DVBv5 enhanced statistics if available;

● It provides decoders for several MPEG-TS descriptors needed to identify the Packet IDs inside a MPEG-TS program;

● Provides functions to read files containing channel/program properties;

● Provides extra statistics like signal quality, BER and PER measurements, etc.


Example: tuning into a channeldvb = dvb_fe_open(0, 0, 0, 0); /* Opens adapter 0, frontend 0 */

dvb_file = dvb_read_file_format(“channel”, SYS_UNDEFINED, FILE_DVBV5);

entry = dvb_file->first_entry; /* Use the first channel */

for (i = 0; i < entry->n_props; i++)

dvb_fe_store_parm(dvb, entry->props[i].cmd, entry->props[i].u.data);

dvb_file_free(dvb_file);

dvb_fe_set_parms(dvb);

while (1) {

char buf[256], p = buf; int len = sizeof(buf), show = 1;

dvb_fe_get_stats(dvb);

dvb_fe_snprintf_stat(dvb, DTV_STATUS, NULL, 0, &p, &len, &show);

dvb_fe_snprintf_stat(dvb, DTV_QUALITY, "Qual", 0, &p, &len, &show);

fprintf(fd, "\t%s\n", buf);

}


DVBv5 utils● DVBv5 utils:

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

– It consists of 4 tools:

● Both DVBv5 utils and libdvbv5 are packaged together withv4l-utils:

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

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, allows to manually set the DVB frontend delivery system and to monitor the frontend statistics

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

Lock (0x1f) Quality= Good Signal= 100.00% C/N= -13.80dB

UCB= 70 postBER= 3.14x10^-3 PER= 0

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

...

Lock (0x1f) Quality= Good Signal= 100.00% C/N= -13.90dB UCB= 384 postBER= 96.8x10^-6 PER= 0

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 for TV on Linux:

– Userspace/kernelspace: [email protected]

● Upstream trees:

– To test Kernel drivers: http://git.linuxtv.org/media_build.git

– To develop Kernel drivers http://git.linuxtv.org/media_tree.git

– v4l-utils, dvbv5 utils and libdvbv5: http://git.linuxtv.org/v4l-utils.git

● Documentation:

– Media APIs http://linuxtv.org/downloads/v4l-dvb-apis

– libdvbv5 docs: http://linuxtv.org/docs/libdvbv5/index.html

● 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/downloads/v4l-dvb-apis

http://linuxtv.org/docs/libdvbv5/index.html

http://linuxtv.org/wiki/

33

Thank you.


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