<title>DVB Demux Device</title>
<para>The DVB demux device controls the filters of the DVB hardware/software. It can be
accessed through <emphasis role="tt">/dev/adapter0/demux0</emphasis>. Data types and and ioctl definitions can be
accessed by including <emphasis role="tt">linux/dvb/dmx.h</emphasis> in your application.
</para>
<section id="dmx_types">
<title>Demux Data Types</title>
<section id="dmx_output_t">
<title>dmx_output_t</title>
<programlisting>
typedef enum
{
DMX_OUT_DECODER,
DMX_OUT_TAP,
DMX_OUT_TS_TAP
} dmx_output_t;
</programlisting>
<para><emphasis role="tt">DMX_OUT_TAP</emphasis> delivers the stream output to the demux device on which the ioctl is
called.
</para>
<para><emphasis role="tt">DMX_OUT_TS_TAP</emphasis> routes output to the logical DVR device <emphasis role="tt">/dev/dvb/adapter0/dvr0</emphasis>,
which delivers a TS multiplexed from all filters for which <emphasis role="tt">DMX_OUT_TS_TAP</emphasis> was
specified.
</para>
</section>
<section id="dmx_input_t">
<title>dmx_input_t</title>
<programlisting>
typedef enum
{
DMX_IN_FRONTEND,
DMX_IN_DVR
} dmx_input_t;
</programlisting>
</section>
<section id="dmx_pes_type_t">
<title>dmx_pes_type_t</title>
<programlisting>
typedef enum
{
DMX_PES_AUDIO,
DMX_PES_VIDEO,
DMX_PES_TELETEXT,
DMX_PES_SUBTITLE,
DMX_PES_PCR,
DMX_PES_OTHER
} dmx_pes_type_t;
</programlisting>
</section>
<section id="dmx_event_t">
<title>dmx_event_t</title>
<programlisting>
typedef enum
{
DMX_SCRAMBLING_EV,
DMX_FRONTEND_EV
} dmx_event_t;
</programlisting>
</section>
<section id="dmx_scrambling_status_t">
<title>dmx_scrambling_status_t</title>
<programlisting>
typedef enum
{
DMX_SCRAMBLING_OFF,
DMX_SCRAMBLING_ON
} dmx_scrambling_status_t;
</programlisting>
</section>
<section id="dmx_filter">
<title>struct dmx_filter</title>
<programlisting>
typedef struct dmx_filter
{
uint8_t filter[DMX_FILTER_SIZE];
uint8_t mask[DMX_FILTER_SIZE];
} dmx_filter_t;
</programlisting>
</section>
<section id="dmx_sct_filter_params">
<title>struct dmx_sct_filter_params</title>
<programlisting>
struct dmx_sct_filter_params
{
uint16_t pid;
dmx_filter_t filter;
uint32_t timeout;
uint32_t flags;
#define DMX_CHECK_CRC 1
#define DMX_ONESHOT 2
#define DMX_IMMEDIATE_START 4
};
</programlisting>
</section>
<section id="dmx_pes_filter_params">
<title>struct dmx_pes_filter_params</title>
<programlisting>
struct dmx_pes_filter_params
{
uint16_t pid;
dmx_input_t input;
dmx_output_t output;
dmx_pes_type_t pes_type;
uint32_t flags;
};
</programlisting>
</section>
<section id="dmx_event">
<title>struct dmx_event</title>
<programlisting>
struct dmx_event
{
dmx_event_t event;
time_t timeStamp;
union
{
dmx_scrambling_status_t scrambling;
} u;
};
</programlisting>
</section>
<section id="dmx_stc">
<title>struct dmx_stc</title>
<programlisting>
struct dmx_stc {
unsigned int num; /⋆ input : which STC? 0..N ⋆/
unsigned int base; /⋆ output: divisor for stc to get 90 kHz clock ⋆/
uint64_t stc; /⋆ output: stc in 'base'⋆90 kHz units ⋆/
};
</programlisting>
</section>
</section>
<section id="dmx_fcalls">
<title>Demux Function Calls</title>
<section id="dmx_fopen">
<title>open()</title>
<para>DESCRIPTION
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>This system call, used with a device name of /dev/dvb/adapter0/demux0,
allocates a new filter and returns a handle which can be used for subsequent
control of that filter. This call has to be made for each filter to be used, i.e. every
returned file descriptor is a reference to a single filter. /dev/dvb/adapter0/dvr0
is a logical device to be used for retrieving Transport Streams for digital
video recording. When reading from this device a transport stream containing
the packets from all PES filters set in the corresponding demux device
(/dev/dvb/adapter0/demux0) having the output set to DMX_OUT_TS_TAP. A
recorded Transport Stream is replayed by writing to this device. </para>
<para>The significance of blocking or non-blocking mode is described in the
documentation for functions where there is a difference. It does not affect the
semantics of the open() call itself. A device opened in blocking mode can later
be put into non-blocking mode (and vice versa) using the F_SETFL command
of the fcntl system call.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>SYNOPSIS
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>int open(const char ⋆deviceName, int flags);</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>PARAMETERS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>const char
*deviceName</para>
</entry><entry
align="char">
<para>Name of demux device.</para>
</entry>
</row><row><entry
align="char">
<para>int flags</para>
</entry><entry
align="char">
<para>A bit-wise OR of the following flags:</para>
</entry>
</row><row><entry
align="char">
</entry><entry
align="char">
<para>O_RDWR read/write access</para>
</entry>
</row><row><entry
align="char">
</entry><entry
align="char">
<para>O_NONBLOCK open in non-blocking mode</para>
</entry>
</row><row><entry
align="char">
</entry><entry
align="char">
<para>(blocking mode is the default)</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>ERRORS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>ENODEV</para>
</entry><entry
align="char">
<para>Device driver not loaded/available.</para>
</entry>
</row><row><entry
align="char">
<para>EINVAL</para>
</entry><entry
align="char">
<para>Invalid argument.</para>
</entry>
</row><row><entry
align="char">
<para>EMFILE</para>
</entry><entry
align="char">
<para>“Too many open files”, i.e. no more filters available.</para>
</entry>
</row><row><entry
align="char">
<para>ENOMEM</para>
</entry><entry
align="char">
<para>The driver failed to allocate enough memory.</para>
</entry>
</row></tbody></tgroup></informaltable>
</section>
<section id="dmx_fclose">
<title>close()</title>
<para>DESCRIPTION
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>This system call deactivates and deallocates a filter that was previously
allocated via the open() call.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>SYNOPSIS
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>int close(int fd);</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>PARAMETERS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>int fd</para>
</entry><entry
align="char">
<para>File descriptor returned by a previous call to open().</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>ERRORS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>EBADF</para>
</entry><entry
align="char">
<para>fd is not a valid open file descriptor.</para>
</entry>
</row></tbody></tgroup></informaltable>
</section>
<section id="dmx_fread">
<title>read()</title>
<para>DESCRIPTION
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>This system call returns filtered data, which might be section or PES data. The
filtered data is transferred from the driver’s internal circular buffer to buf. The
maximum amount of data to be transferred is implied by count.</para>
</entry>
</row><row><entry
align="char">
<para>When returning section data the driver always tries to return a complete single
section (even though buf would provide buffer space for more data). If the size
of the buffer is smaller than the section as much as possible will be returned,
and the remaining data will be provided in subsequent calls.</para>
</entry>
</row><row><entry
align="char">
<para>The size of the internal buffer is 2 * 4096 bytes (the size of two maximum
sized sections) by default. The size of this buffer may be changed by using the
DMX_SET_BUFFER_SIZE function. If the buffer is not large enough, or if
the read operations are not performed fast enough, this may result in a buffer
overflow error. In this case EOVERFLOW will be returned, and the circular
buffer will be emptied. This call is blocking if there is no data to return, i.e. the
process will be put to sleep waiting for data, unless the O_NONBLOCK flag
is specified.</para>
</entry>
</row><row><entry
align="char">
<para>Note that in order to be able to read, the filtering process has to be started
by defining either a section or a PES filter by means of the ioctl functions,
and then starting the filtering process via the DMX_START ioctl function
or by setting the DMX_IMMEDIATE_START flag. If the reading is done
from a logical DVR demux device, the data will constitute a Transport Stream
including the packets from all PES filters in the corresponding demux device
/dev/dvb/adapter0/demux0 having the output set to DMX_OUT_TS_TAP.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>SYNOPSIS
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>size_t read(int fd, void ⋆buf, size_t count);</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>PARAMETERS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>int fd</para>
</entry><entry
align="char">
<para>File descriptor returned by a previous call to open().</para>
</entry>
</row><row><entry
align="char">
<para>void *buf</para>
</entry><entry
align="char">
<para>Pointer to the buffer to be used for returned filtered data.</para>
</entry>
</row><row><entry
align="char">
<para>size_t count</para>
</entry><entry
align="char">
<para>Size of buf.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>ERRORS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>EWOULDBLOCK</para>
</entry><entry
align="char">
<para>No data to return and O_NONBLOCK was specified.</para>
</entry>
</row><row><entry
align="char">
<para>EBADF</para>
</entry><entry
align="char">
<para>fd is not a valid open file descriptor.</para>
</entry>
</row><row><entry
align="char">
<para>ECRC</para>
</entry><entry
align="char">
<para>Last section had a CRC error - no data returned. The
buffer is flushed.</para>
</entry>
</row><row><entry
align="char">
<para>EOVERFLOW</para>
</entry><entry
align="char">
</entry>
</row><row><entry
align="char">
</entry><entry
align="char">
<para>The filtered data was not read from the buffer in due
time, resulting in non-read data being lost. The buffer is
flushed.</para>
</entry>
</row><row><entry
align="char">
<para>ETIMEDOUT</para>
</entry><entry
align="char">
<para>The section was not loaded within the stated timeout
period. See ioctl DMX_SET_FILTER for how to set a
timeout.</para>
</entry>
</row><row><entry
align="char">
<para>EFAULT</para>
</entry><entry
align="char">
<para>The driver failed to write to the callers buffer due to an
invalid *buf pointer.</para>
</entry>
</row></tbody></tgroup></informaltable>
</section>
<section id="dmx_fwrite">
<title>write()</title>
<para>DESCRIPTION
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>This system call is only provided by the logical device /dev/dvb/adapter0/dvr0,
associated with the physical demux device that provides the actual DVR
functionality. It is used for replay of a digitally recorded Transport Stream.
Matching filters have to be defined in the corresponding physical demux
device, /dev/dvb/adapter0/demux0. The amount of data to be transferred is
implied by count.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>SYNOPSIS
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>ssize_t write(int fd, const void ⋆buf, size_t
count);</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>PARAMETERS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>int fd</para>
</entry><entry
align="char">
<para>File descriptor returned by a previous call to open().</para>
</entry>
</row><row><entry
align="char">
<para>void *buf</para>
</entry><entry
align="char">
<para>Pointer to the buffer containing the Transport Stream.</para>
</entry>
</row><row><entry
align="char">
<para>size_t count</para>
</entry><entry
align="char">
<para>Size of buf.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>ERRORS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>EWOULDBLOCK</para>
</entry><entry
align="char">
<para>No data was written. This
might happen if O_NONBLOCK was specified and there
is no more buffer space available (if O_NONBLOCK is
not specified the function will block until buffer space is
available).</para>
</entry>
</row><row><entry
align="char">
<para>EBUSY</para>
</entry><entry
align="char">
<para>This error code indicates that there are conflicting
requests. The corresponding demux device is setup to
receive data from the front- end. Make sure that these
filters are stopped and that the filters with input set to
DMX_IN_DVR are started.</para>
</entry>
</row><row><entry
align="char">
<para>EBADF</para>
</entry><entry
align="char">
<para>fd is not a valid open file descriptor.</para>
</entry>
</row></tbody></tgroup></informaltable>
</section>
<section id="dmx_start">
<title>DMX_START</title>
<para>DESCRIPTION
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>This ioctl call is used to start the actual filtering operation defined via the ioctl
calls DMX_SET_FILTER or DMX_SET_PES_FILTER.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>SYNOPSIS
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>int ioctl( int fd, int request = DMX_START);</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>PARAMETERS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>int fd</para>
</entry><entry
align="char">
<para>File descriptor returned by a previous call to open().</para>
</entry>
</row><row><entry
align="char">
<para>int request</para>
</entry><entry
align="char">
<para>Equals DMX_START for this command.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>ERRORS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>EBADF</para>
</entry><entry
align="char">
<para>fd is not a valid file descriptor.</para>
</entry>
</row><row><entry
align="char">
<para>EINVAL</para>
</entry><entry
align="char">
<para>Invalid argument, i.e. no filtering parameters provided via
the DMX_SET_FILTER or DMX_SET_PES_FILTER
functions.</para>
</entry>
</row><row><entry
align="char">
<para>EBUSY</para>
</entry><entry
align="char">
<para>This error code indicates that there are conflicting
requests. There are active filters filtering data from
another input source. Make sure that these filters are
stopped before starting this filter.</para>
</entry>
</row></tbody></tgroup></informaltable>
</section>
<section id="dmx_stop">
<title>DMX_STOP</title>
<para>DESCRIPTION
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>This ioctl call is used to stop the actual filtering operation defined via the
ioctl calls DMX_SET_FILTER or DMX_SET_PES_FILTER and started via
the DMX_START command.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>SYNOPSIS
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>int ioctl( int fd, int request = DMX_STOP);</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>PARAMETERS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>int fd</para>
</entry><entry
align="char">
<para>File descriptor returned by a previous call to open().</para>
</entry>
</row><row><entry
align="char">
<para>int request</para>
</entry><entry
align="char">
<para>Equals DMX_STOP for this command.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>ERRORS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>EBADF</para>
</entry><entry
align="char">
<para>fd is not a valid file descriptor.</para>
</entry>
</row></tbody></tgroup></informaltable>
</section>
<section id="dmx_set_filter">
<title>DMX_SET_FILTER</title>
<para>DESCRIPTION
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>This ioctl call sets up a filter according to the filter and mask parameters
provided. A timeout may be defined stating number of seconds to wait for a
section to be loaded. A value of 0 means that no timeout should be applied.
Finally there is a flag field where it is possible to state whether a section should
be CRC-checked, whether the filter should be a ”one-shot” filter, i.e. if the
filtering operation should be stopped after the first section is received, and
whether the filtering operation should be started immediately (without waiting
for a DMX_START ioctl call). If a filter was previously set-up, this filter will
be canceled, and the receive buffer will be flushed.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>SYNOPSIS
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>int ioctl( int fd, int request = DMX_SET_FILTER,
struct dmx_sct_filter_params ⋆params);</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>PARAMETERS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>int fd</para>
</entry><entry
align="char">
<para>File descriptor returned by a previous call to open().</para>
</entry>
</row><row><entry
align="char">
<para>int request</para>
</entry><entry
align="char">
<para>Equals DMX_SET_FILTER for this command.</para>
</entry>
</row><row><entry
align="char">
<para>struct
dmx_sct_filter_params
*params</para>
</entry><entry
align="char">
<para>Pointer to structure containing filter parameters.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>ERRORS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>EBADF</para>
</entry><entry
align="char">
<para>fd is not a valid file descriptor.</para>
</entry>
</row><row><entry
align="char">
<para>EINVAL</para>
</entry><entry
align="char">
<para>Invalid argument.</para>
</entry>
</row></tbody></tgroup></informaltable>
</section>
<section id="dmx_set_pes_filter">
<title>DMX_SET_PES_FILTER</title>
<para>DESCRIPTION
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>This ioctl call sets up a PES filter according to the parameters provided. By a
PES filter is meant a filter that is based just on the packet identifier (PID), i.e.
no PES header or payload filtering capability is supported.</para>
</entry>
</row><row><entry
align="char">
<para>The transport stream destination for the filtered output may be set. Also the
PES type may be stated in order to be able to e.g. direct a video stream directly
to the video decoder. Finally there is a flag field where it is possible to state
whether the filtering operation should be started immediately (without waiting
for a DMX_START ioctl call). If a filter was previously set-up, this filter will
be cancelled, and the receive buffer will be flushed.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>SYNOPSIS
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>int ioctl( int fd, int request = DMX_SET_PES_FILTER,
struct dmx_pes_filter_params ⋆params);</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>PARAMETERS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>int fd</para>
</entry><entry
align="char">
<para>File descriptor returned by a previous call to open().</para>
</entry>
</row><row><entry
align="char">
<para>int request</para>
</entry><entry
align="char">
<para>Equals DMX_SET_PES_FILTER for this command.</para>
</entry>
</row><row><entry
align="char">
<para>struct
dmx_pes_filter_params
*params</para>
</entry><entry
align="char">
<para>Pointer to structure containing filter parameters.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>ERRORS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>EBADF</para>
</entry><entry
align="char">
<para>fd is not a valid file descriptor.</para>
</entry>
</row><row><entry
align="char">
<para>EINVAL</para>
</entry><entry
align="char">
<para>Invalid argument.</para>
</entry>
</row><row><entry
align="char">
<para>EBUSY</para>
</entry><entry
align="char">
<para>This error code indicates that there are conflicting
requests. There are active filters filtering data from
another input source. Make sure that these filters are
stopped before starting this filter.</para>
</entry>
</row></tbody></tgroup></informaltable>
</section>
<section id="dms_set_buffer_size">
<title>DMX_SET_BUFFER_SIZE</title>
<para>DESCRIPTION
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>This ioctl call is used to set the size of the circular buffer used for filtered data.
The default size is two maximum sized sections, i.e. if this function is not called
a buffer size of 2 * 4096 bytes will be used.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>SYNOPSIS
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>int ioctl( int fd, int request =
DMX_SET_BUFFER_SIZE, unsigned long size);</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>PARAMETERS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>int fd</para>
</entry><entry
align="char">
<para>File descriptor returned by a previous call to open().</para>
</entry>
</row><row><entry
align="char">
<para>int request</para>
</entry><entry
align="char">
<para>Equals DMX_SET_BUFFER_SIZE for this command.</para>
</entry>
</row><row><entry
align="char">
<para>unsigned long size</para>
</entry><entry
align="char">
<para>Size of circular buffer.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>ERRORS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>EBADF</para>
</entry><entry
align="char">
<para>fd is not a valid file descriptor.</para>
</entry>
</row><row><entry
align="char">
<para>ENOMEM</para>
</entry><entry
align="char">
<para>The driver was not able to allocate a buffer of the
requested size.</para>
</entry>
</row></tbody></tgroup></informaltable>
</section>
<section id="dmx_get_event">
<title>DMX_GET_EVENT</title>
<para>DESCRIPTION
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>This ioctl call returns an event if available. If an event is not available,
the behavior depends on whether the device is in blocking or non-blocking
mode. In the latter case, the call fails immediately with errno set to
EWOULDBLOCK. In the former case, the call blocks until an event becomes
available.</para>
</entry>
</row><row><entry
align="char">
<para>The standard Linux poll() and/or select() system calls can be used with the
device file descriptor to watch for new events. For select(), the file descriptor
should be included in the exceptfds argument, and for poll(), POLLPRI should
be specified as the wake-up condition. Only the latest event for each filter is
saved.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>SYNOPSIS
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>int ioctl( int fd, int request = DMX_GET_EVENT,
struct dmx_event ⋆ev);</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>PARAMETERS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>int fd</para>
</entry><entry
align="char">
<para>File descriptor returned by a previous call to open().</para>
</entry>
</row><row><entry
align="char">
<para>int request</para>
</entry><entry
align="char">
<para>Equals DMX_GET_EVENT for this command.</para>
</entry>
</row><row><entry
align="char">
<para>struct dmx_event *ev</para>
</entry><entry
align="char">
<para>Pointer to the location where the event is to be stored.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>ERRORS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>EBADF</para>
</entry><entry
align="char">
<para>fd is not a valid file descriptor.</para>
</entry>
</row><row><entry
align="char">
<para>EFAULT</para>
</entry><entry
align="char">
<para>ev points to an invalid address.</para>
</entry>
</row><row><entry
align="char">
<para>EWOULDBLOCK</para>
</entry><entry
align="char">
<para>There is no event pending, and the device is in
non-blocking mode.</para>
</entry>
</row></tbody></tgroup></informaltable>
</section>
<section id="dmx_get_stc">
<title>DMX_GET_STC</title>
<para>DESCRIPTION
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>This ioctl call returns the current value of the system time counter (which is driven
by a PES filter of type DMX_PES_PCR). Some hardware supports more than one
STC, so you must specify which one by setting the num field of stc before the ioctl
(range 0...n). The result is returned in form of a ratio with a 64 bit numerator
and a 32 bit denominator, so the real 90kHz STC value is stc->stc /
stc->base
.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>SYNOPSIS
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>int ioctl( int fd, int request = DMX_GET_STC, struct
dmx_stc ⋆stc);</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>PARAMETERS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>int fd</para>
</entry><entry
align="char">
<para>File descriptor returned by a previous call to open().</para>
</entry>
</row><row><entry
align="char">
<para>int request</para>
</entry><entry
align="char">
<para>Equals DMX_GET_STC for this command.</para>
</entry>
</row><row><entry
align="char">
<para>struct dmx_stc *stc</para>
</entry><entry
align="char">
<para>Pointer to the location where the stc is to be stored.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>ERRORS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>EBADF</para>
</entry><entry
align="char">
<para>fd is not a valid file descriptor.</para>
</entry>
</row><row><entry
align="char">
<para>EFAULT</para>
</entry><entry
align="char">
<para>stc points to an invalid address.</para>
</entry>
</row><row><entry
align="char">
<para>EINVAL</para>
</entry><entry
align="char">
<para>Invalid stc number.</para>
</entry>
</row></tbody></tgroup></informaltable>
</section></section>
