Welcome to DVBlast!

DVBlast is a simple and powerful MPEG-2/TS demux and streaming application with several input methods:

• linux-dvb-supported cards (DVB-S, DVB-S2, DVB-C, DVB-T...)
• DVB-ASI cards
• UDP or RTP stream carrying a transport stream

It outputs one or several RTP streams carrying transport streams with:

• hardware or software PID filtering
• PID-based or service-based demultiplexing
• optional descrambling via CAM device
• optional DVB tables

DVBlast is written to be the core of a custom IRD, CID,or ASI gateway, based on a PC with a Linux-supported card. It is very lightweight and stable, designed for 24/7 operation.

Current features

• Lightweight program designed for extreme memory and CPU conditions
• No runtime dependancy; one build dependancy (biTStream)
• CAM menus (MMI) support via an external application
• The configuration file describing outputs can be reloaded without losing a single packet
• Support for the new S2API of linux-dvb
• IPv6 network support
• UDP rather than RTP output for IPTV STBs which don't support RTP

Tuning DVBlast

You usually want to supply DVBlast with the parameters of a transponder, for instance for DVB-S :

dvblast -f 11570000 -s 27500000 -v 18

This tunes to frequency 11570 MHz, symbol rate 27500, horizontal (-v 18).

For DVB-S2 you must indicate a modulation with -m qpsk|psk_8|apsk_16|apsk_32.

For DVB-T you must indicate a bandwidth, usually -b 8 for 8 MHz multiplexes.

Please note that frequencies are in kHz for DVB-S/S2/C, but Hz for DVB-T. Symbol rates are in symbols/s, and bandwidths in MHz. If you have several linux-dvb cards in the machine, specify which one to use with -a.

You generally want to run DVBlast in DVB compliance mode with option -C. This option will pass through or generate mandatory DVB tables (NIT, SDT, EITp/f, TOT, TDT). If you also want to pass-through the EIT schedule tables, use the -e switch. It is considered a good practice to configure the name of the network (for the NIT) with the -M option.

If you don't want to set these options on a general basis, you can set them per output - see below.

Other rarely used options are available - run dvblast -h for more information.

Alternative inputs

DVBlast may handle several DVB adapters in the same machine with the -a switch: -a 3 will use /dev/dvb/adapter3. Additionally, selecting between frontends on a single card is supported with the -n switch. This is useful for hybrid DVB/S + DVB/T cards.

If you own a Computer Modules DVB-ASI input card, you can have DVBlast filter and demultiplex the inputs. You just need to specify the slot number with -A.

If you own a Deltacast ASI input card, you can have DVBlast filter and demultiplex the inputs. You just need to specify the input as "-A deltacast:" where is 100 * the card number (0 based) + the channel number (0 based).

DVBlast can also read from a UDP or RTP IPv4 source carrying for instance a multi-program transport stream. The address is specified with -D. See the 'advanced features' section for information on how to create such a stream for instance to cross network boundaries between the receivers and the target network.

The syntax of the -D option is: [[:]@][:][/]* where is the multicast address carrying the stream, and is optionally the address of the source, for source-specific multicast. Options include: /udp (for streams without an RTP header) /mtu=XXXX (sets the maximum UDP packet size) /ifindex=X (binds to a specific network interface, by link number) /ifaddr=XXX.XXX.XXX.XXX (binds to a specific network interface, by address)

For example: -D 239.255.0.2:1234/udp/ifindex=1

Configuring outputs

DVBlast reads a configuration file containing one or several lines in the format : [:][@[:]][/]* [,]*

For instance : 239.255.0.1:1234 1 10750 1234,1235,1236

The configuration file can be reloaded by sending "HUP" to the program, or via the dvblastctl program.

IPv6 is supported, the destination address must be specified in the format described by RFC2732. When using link-local scope addresses, it is mandatory to include the interface name in the address, as shown in the example below. If you do not include the interface name, you will see an "invalid argument" error. The interface name is optional for site-local and global scope addresses.

For example : [ff12::1%eth0]:1234 1 10750 [ff15::abcd]:1234 1 10750

An optional bind address can be specified after an '@' sign. The typical usage of this is to allow binding to a specific interface in a system which has several. For instance: 239.255.0.1:[email protected] 1 10750

For IPv6 the bind address is not relevant; binding to an interface is achieved via the option "/ifindex=X" where X is the number of the link, as given by the command ip link.

The "always on" flag tells DVBlast whether the channel is expected to be on at all times or if it may break. If set to "1", then DVBlast will regularly reset the CAM module if it fails to descramble the service, assuming the module is dead. Every time it is reset a few TS packets will be lost, that is why this feature is optional.

Other options can be set by appending / to the multicast address definition. Available options include : /udp (turns on -U for a specific output) /dvb (turns on -C for a specific output) /epg (turns on -C -e for a specific output) /tsid=XXX (sets the transport stream ID) /ssrc=XXX.XXX.XXX.XXX (sets the RTP synchronization source IPv4) /retention=XXX (see -E) /latency=XXX (see -L) /ttl=XX (see -t) /tos=XX (sets the IPv4 Type Of Service option) /mtu=XXXX (sets the maximum UDP packet size) /srvname=Some_Channel (set service name in SDT) /srvprovider=Some_Provider (set provider name in SDT) /pidmap=pmt_pid,audio_pid,video_pid,spu_pid /newsid=XX (set output service ID) /srcaddr=XXX.XXX.XXX.XXX (use RAW packets and set source IPv4) /srcport=XX (set source port, depends on /srcaddr)

When setting text options like /srvname or /srvprovider, remember that the underscore character (_) will be replaced by space ( ).

Several options can be appended, for instance:

239.255.0.1:1234/udp/epg/tsid=42/ssrc=192.168.0.1

The optional "/udp" parameter can be used to force DVBlast to output raw UDP stream. This functionality is provided for backwards compatibility with IPTV set top boxes that don't support RTP and should only be used if absolutely necessary. If you need both RTP and UDP streams of the same program, specify them on separate lines like this:

239.255.0.1:1234 1 10750 239.255.0.2:1234/udp 1 10750

There are three ways of configuring the PIDs to stream :

1. SID-based

239.255.0.1:1234 1 10750

DVBlast will stream all known PIDs from service 10750 (video, audio, and subtitles). The resulting stream is fully MPEG-compliant, with PAT and PMT.

2. SID and PIDs

239.255.0.1:1234 1 10750 1234,1235

DVBlast will stream SID 10750, but only PID 1234 and 1235 will be output. Other known PIDs will be discarded and removed from the PMT. The list of PIDs in the config file does not include the PAT and PMT, but it must include the PCR PID if it is different from the video or audio PID, otherwise the stream won't be compliant.

3. PIDs only

239.255.0.1:1234 1 0 0,128,1234,1235

DVBlast will only stream the PIDs passed. No PAT and PMT will be generated, so if they are not included the stream won't be compliant. Also the included PAT and PMT may contain ghost programs or ESes.

4. PID remapping

239.255.0.1:1234/udp/epg/tsid=42/ssrc=192.168.0.1/pidmap=pmt_pid,audio_pid,video_pid,spu_pid

All four PIDs are required!

Note that the CAM will not be programmed in that case (unless it has been programmed by another line of the config file).

5. Pass-through

239.255.0.1:1234 1 *

The entire received stream will be passed through the output. Please bear in mind that when reading from a DVB adapter, hardware PID filtering is used by default, so not all packets will be output unless you specify the -u option.

The file is read from the command-line :

dvblast -c /tmp/dvblast.conf

Buffering

DVB cards usually output packets in big chunks. This can be problematic with low bitrate multiplexes. By default, DVBlast bufferizes 200 ms and tries to smooth the output. It may be desired to change this value with the -L option. The appropriate value for the output latency should be : chunk_size / multiplex_bitrate

The chunk size for saa7146-based cards is 512000 bits ; for cx23885-based cards is 192512 bits. The chunk size can be modified with an appropriate kernel patch (see extra/). The multiplex_bitrate depends on the symbol rate and many other factors such as the modulation.

The current default value allows for multiplex_rates as low as 2.56 Mbi/s. Smaller multiplexes are rare but exist, so in that case you may want to increase the buffer size. A typical DVB multiplex is 30 or 40 Mbi/s, so the default introduces a superfluous latency ; the buffer can be lowered to 50 ms if latency is an issue.

DVBlast also has another parameter called "max retention time" (-E). This controls how TS packets are grouped together in IP datagrams : the difference between the theorical output times of the first and the last TS packets cannot exceed the maximal retention time.

IP datagrams are normally output at the output time of the earliest TS packet ; it implies that the next TS packets are sent too soon and must be buffered at the receiver level. ISO/IEC 13818-1 makes no provision for this, since IP wasn't in mind when designing TS, so in theory we risk a buffer overflow.

However normal IP receivers feature a jitter buffer which can absorb the overflow ; DVB recommends a 50 ms buffer. DVBlast's default maximal retention time is just below, at 40 ms, which should be fine in most situations.

If some anal set-top-box complains about buffer overflows or clock issues, you may try to lower the value ; the drawback is that on low bitrate streams it will introduce padding. People with low bitrate streams and nice receivers with big buffers can raise this value to avoid superfluous padding and lower the total bitrate.

Please bear in mind though that setting a value for max retention time greater than the output latency has no effect.

Monitoring

If dvblast is run with the -r option, the dvblastctl program can be used to retrieve information from DVBlast about the front-end or CAM module.

dvblastctl -r /tmp/dvblast.sock fe_status dvblastctl -r /tmp/dvblast.sock mmi_status dvblastctl -r /tmp/dvblast.sock shutdown

CAM menu

For easier access to the CAM menus, the dvblast_mmi.sh shell script is provided :

dvblast_mmi.sh -r /tmp/dvblast.sock

Advanced features

For better latency, run DVBlast in real-time priority: -i 1 (requires root privileges).

DVBlast can also stream the entire transponder to an IPv4 or IPv6 address : dvblast -u -d 172.16.42.42:1235 -f 11570000 -s 27500000 -v 18 dvblast -u -d [fe80::0ca:feff:fec0:ffee]:1235 -f 11570000 -s 27500000 -v 18

Note that IPv6 addresses specified on command line may need to have the square brackets escaped ([ and ]), depending on your shell.

The -u switch disables the PID filters, so that all PIDs, even the unused ones, can be output.

Other options are self-understandable, and are listed in dvblast -h.