Trac Configuration File:
xingmux adds a Xing header to MP3 files. This contains information about the duration and size
of the file and a seek table and is very useful for getting an almost correct duration and better
seeking on VBR MP3 files.
This element will remove any existing Xing, LAME or VBRI headers from the beginning of the file.
Pad templates and the element details are registered with the plugin during the gst_xing_mux_base_init()
GStreamer uses a type system to ensure that the data passed between elements is in a recognized format
pad templates are registered during the gst_xing_mux_base_init () function. Pads are created from these
templates in the gst_xing_mux_init () function using gst_pad_new_from_template (). The
template can be retrieved from the element class using gst_element_class_get_pad_template()
method 1 and 2 are doing the same, but what's the difference?
1. GstElementClass *klass = GST_ELEMENT_CLASS (xingmux_class); gst_pad_new_from_template (gst_element_class_get_pad_template (klass,"sink"), "sink"); gst_pad_new_from_template (gst_element_class_get_pad_template (klass,"src"), "src"); 2. gst_pad_new_from_static_template (&gst_xing_mux_sink_template, "sink"); gst_pad_new_from_static_template (&gst_xing_mux_src_template, "src");
xingmux has a sinkpad and a srcpad, it supports mpeg version 1 audio, layer 1 to 3,
any channel at any samplerate
85 static GstStaticPadTemplate gst_xing_mux_sink_template =
86 GST_STATIC_PAD_TEMPLATE ("sink",
87 GST_PAD_SINK,
88 GST_PAD_ALWAYS,
89 GST_STATIC_CAPS ("audio/mpeg, "
90 "mpegversion = (int) 1, " "layer = (int) [ 1, 3 ]"));
initialise the class only once during the gst_xing_mux_class_init()
(specifying what signals, arguments and virtual functions the class has and setting up global state)
The primary and most important way of controlling how an element behaves, is through GObject
properties. GObject properties are defined in the _class_init () function.
gst_xing_mux_init()
Test Pipeline:gst-launch-0.10 filesrc location=test.mp3 ! xingmux ! filesink location=test2.mp3
additional: function plugin_init() register the element when the plugin is loaded, is in the source file plugin.c under the same folder gst-plugins-ugly/gst/mpegaudioparse
Frist some introduce words:
absolute_time: the current time get from GstClock (monotonically increasing time)
running_time:the total time spent in the PLAYING state
base_time:defined as the absolute_time minus the running_time at the time when the pipeline is set to PLAYING
stream_time:the position in the stream(between 0 and the total duration)
GStreamer can use different clocks:
time is always expessed in nanoseconds, so I think there must have a conversion between different time types.
pipeline state and running_time:
The GstBuffer timestamps and the preceeding NEW_SEGMENT event define a transformation of the buffer timestamps to running_time
B: GstBuffer
NS: NEWSEGMENT event preceeding the buffers
if (NS.rate > 0.0)
B.running_time = (B.timestamp - NS.start) / NS.abs_rate + NS.accum
else
B.running_time = (NS.stop - B.timestamp) / NS.abs_rate + NS.accum
There are two ways to get the running_time:
Kernel measures the passage of the time in three different ways:
| Name | second | Microsecond | Nanosecond |
|---|---|---|---|
| Getting the current time of day | time() | gettimeofday() | clock_gettime() |
| Setting the current time of day | stime() | settimeofday() | clock_settime() |
| Sleeping | sleep() | usleep() | nanosleep() |
Now Microsoft, ipod nano are in my mind, are these names from here? So interesting.
With a 32-bit long type, time_t will let us have the Y2K mess all over again --- in 2038!
and "Come 22:14:07 on Monday, 18 January 2038, most systems and software will be 64-bit." said Robert Love. Will these happen, let's go and see.
POSIX Clocks have four of the linux standard time source:
make looks at the file modification timestamps of the source file versus the object file. If the source file is newer than the object file, make rebuilds the source file into an updated object file.If the source file is not newer than the object, however, no action is taken
This is my second time to read GStreamer Application Development Manual
Record something important
| Type | Details | Number of pads |
|---|---|---|
| Source elements | do not accept data, only generate data | a source pad |
| Filters and filter-like elements | operate the data | at least one input and one output pads |
| Sink elements | accept data and do not produce anything | a sink pad |
#include <gst/gst.h>
int main (int argc, char *argv[])
{
GstElement *element;
/* init GStreamer */
gst_init (&argc, &argv);
/* create element */
element = gst_element_factory_make ("fakesrc", "source");
if (!element) {
g_print ("Failed to create element of type ’fakesrc’\n");
return -1;
}
gst_object_unref (GST_OBJECT (element));
return 0;
}
| Name | Details |
|---|---|
| Error, warning and information notifications | those are used by elements if a message should be shown to the user about the state of the pipeline |
| End-of-stream notification | emitted when the stream has ended |
| Tags | emitted when metadata was found in the stream |
| State-changes | emitted after a successful state change |
| Buffering | emitted during caching of network-streams |
| Element messages | these are special messages that are unique to certain elements and usually represent additional features |
| Application-specific messages | any information on those can be extracted by getting the message |structure (see above) and reading its fields |
| Number | Name | Description |
|---|---|---|
| 1 | Poniter | A pointer to a piece of memory |
| 2 | Size | The size of the memory |
| 3 | Timestamp | A timestamp for the buffer |
| 4 | refcount | A refcount that indicates how many elements are using this buffer, This refcount will be used to destroy the buffer when no element has a reference to it |
| 5 | Flags | Buffer flags |
Get more information here