3.1. Demux Data Types¶

enum dmx_output¶: Output for the demux.

Constants

DMX_OUT_DECODER

Streaming directly to decoder.

DMX_OUT_TAP

Output going to a memory buffer (to be retrieved via the read command). Delivers the stream output to the demux device on which the ioctl is called.

DMX_OUT_TS_TAP

Output multiplexed into a new TS (to be retrieved by reading from the logical DVR device). Routes output to the logical DVR device /dev/dvb/adapter?/dvr?, which delivers a TS multiplexed from all filters for which DMX_OUT_TS_TAP was specified.

DMX_OUT_TSDEMUX_TAP

Like DMX_OUT_TS_TAP but retrieved from the DMX device.

enum dmx_input¶: Input from the demux.

Constants

DMX_IN_FRONTEND: Input from a front-end device.
DMX_IN_DVR: Input from the logical DVR device.

enum dmx_ts_pes¶: type of the PES filter.

Constants

DMX_PES_AUDIO0: first audio PID. Also referred as DMX_PES_AUDIO.
DMX_PES_VIDEO0: first video PID. Also referred as DMX_PES_VIDEO.
DMX_PES_TELETEXT0: first teletext PID. Also referred as DMX_PES_TELETEXT.
DMX_PES_SUBTITLE0: first subtitle PID. Also referred as DMX_PES_SUBTITLE.
DMX_PES_PCR0: first Program Clock Reference PID. Also referred as DMX_PES_PCR.
DMX_PES_AUDIO1: second audio PID.
DMX_PES_VIDEO1: second video PID.
DMX_PES_TELETEXT1: second teletext PID.
DMX_PES_SUBTITLE1: second subtitle PID.
DMX_PES_PCR1: second Program Clock Reference PID.
DMX_PES_AUDIO2: third audio PID.
DMX_PES_VIDEO2: third video PID.
DMX_PES_TELETEXT2: third teletext PID.
DMX_PES_SUBTITLE2: third subtitle PID.
DMX_PES_PCR2: third Program Clock Reference PID.
DMX_PES_AUDIO3: fourth audio PID.
DMX_PES_VIDEO3: fourth video PID.
DMX_PES_TELETEXT3: fourth teletext PID.
DMX_PES_SUBTITLE3: fourth subtitle PID.
DMX_PES_PCR3: fourth Program Clock Reference PID.
DMX_PES_OTHER: any other PID.

struct dmx_filter¶: Specifies a section header filter.

Definition:

struct dmx_filter {
    __u8 filter[DMX_FILTER_SIZE];
    __u8 mask[DMX_FILTER_SIZE];
    __u8 mode[DMX_FILTER_SIZE];
};

Members

filter: bit array with bits to be matched at the section header.
mask: bits that are valid at the filter bit array.
mode: mode of match: if bit is zero, it will match if equal (positive match); if bit is one, it will match if the bit is negated.

Note

All arrays in this struct have a size of DMX_FILTER_SIZE (16 bytes).

struct dmx_sct_filter_params¶: Specifies a section filter.

Definition:

struct dmx_sct_filter_params {
    __u16 pid;
    struct dmx_filter filter;
    __u32 timeout;
    __u32 flags;
#define DMX_CHECK_CRC       1;
#define DMX_ONESHOT         2;
#define DMX_IMMEDIATE_START 4;
};

Members

pid: PID to be filtered.
filter: section header filter, as defined by struct dmx_filter.
timeout: maximum time to filter, in milliseconds.
flags: extra flags for the section filter.

Description

Carries the configuration for a MPEG-TS section filter.

The flags can be:

DMX_CHECK_CRC - only deliver sections where the CRC check succeeded;

DMX_ONESHOT - disable the section filter after one section has been delivered;

DMX_IMMEDIATE_START - Start filter immediately without requiring a DMX_START.

struct dmx_pes_filter_params¶: Specifies Packetized Elementary Stream (PES) filter parameters.

Definition:

struct dmx_pes_filter_params {
    __u16 pid;
    enum dmx_input  input;
    enum dmx_output output;
    enum dmx_ts_pes pes_type;
    __u32 flags;
};

Members

pid: PID to be filtered.
input: Demux input, as specified by enum dmx_input.
output: Demux output, as specified by enum dmx_output.
pes_type: Type of the pes filter, as specified by enum dmx_pes_type.
flags: Demux PES flags.

struct dmx_stc¶: Stores System Time Counter (STC) information.

Definition:

struct dmx_stc {
    unsigned int num;
    unsigned int base;
    __u64 stc;
};

Members

num: input data: number of the STC, from 0 to N.
base: output: divisor for STC to get 90 kHz clock.
stc: output: stc in base * 90 kHz units.

enum dmx_buffer_flags¶: DMX memory-mapped buffer flags

Constants

DMX_BUFFER_FLAG_HAD_CRC32_DISCARD

Indicates that the Kernel discarded one or more frames due to wrong CRC32 checksum.

DMX_BUFFER_FLAG_TEI

Indicates that the Kernel has detected a Transport Error indicator (TEI) on a filtered pid.

DMX_BUFFER_PKT_COUNTER_MISMATCH

Indicates that the Kernel has detected a packet counter mismatch on a filtered pid.

DMX_BUFFER_FLAG_DISCONTINUITY_DETECTED

Indicates that the Kernel has detected one or more frame discontinuity.

DMX_BUFFER_FLAG_DISCONTINUITY_INDICATOR

Received at least one packet with a frame discontinuity indicator.

struct dmx_buffer¶: dmx buffer info

Definition:

struct dmx_buffer {
    __u32 index;
    __u32 bytesused;
    __u32 offset;
    __u32 length;
    __u32 flags;
    __u32 count;
};

Members

index: id number of the buffer
bytesused: number of bytes occupied by data in the buffer (payload);
offset: for buffers with memory == DMX_MEMORY_MMAP; offset from the start of the device memory for this plane, (or a “cookie” that should be passed to mmap() as offset)
length: size in bytes of the buffer
flags: bit array of buffer flags as defined by enum dmx_buffer_flags. Filled only at DMX_DQBUF.
count: monotonic counter for filled buffers. Helps to identify data stream loses. Filled only at DMX_DQBUF.

Description

Contains data exchanged by application and driver using one of the streaming I/O methods.

Please notice that, for DMX_QBUF, only index should be filled. On DMX_DQBUF calls, all fields will be filled by the Kernel.

struct dmx_requestbuffers¶: request dmx buffer information

Definition:

struct dmx_requestbuffers {
    __u32 count;
    __u32 size;
};

Members

count: number of requested buffers,
size: size in bytes of the requested buffer

Description

Contains data used for requesting a dmx buffer. All reserved fields must be set to zero.

struct dmx_exportbuffer¶: export of dmx buffer as DMABUF file descriptor

Definition:

struct dmx_exportbuffer {
    __u32 index;
    __u32 flags;
    __s32 fd;
};

Members

index: id number of the buffer
flags: flags for newly created file, currently only O_CLOEXEC is supported, refer to manual of open syscall for more details
fd: file descriptor associated with DMABUF (set by driver)

Description

Contains data used for exporting a dmx buffer as DMABUF file descriptor. The buffer is identified by a ‘cookie’ returned by DMX_QUERYBUF (identical to the cookie used to mmap() the buffer to userspace). All reserved fields must be set to zero. The field reserved0 is expected to become a structure ‘type’ allowing an alternative layout of the structure content. Therefore this field should not be used for any other extensions.

The Linux Kernel

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3.1. Demux Data Types¶