如何从 GStreamer 管道读取数据中的特定字段？
How do I read a specific field in data from a GStreamer Pipeline?
目前，我正在 Linux 环境中使用 udp 将视频从摄像机流式传输到 windows 笔记本电脑。
我正在尝试从 rtph264pay 元素的输出中读取序列号。
我的管道正常工作，并且添加了一个焊盘探针。我不知道如何从数据中读取特定字段，特别是缓冲区中的序列号字段。我该怎么做？
我试图查看缓冲区的元数据中是否有内容。我找不到与缓冲区关联的任何元数据（那是因为 while 循环中没有执行任何内容）。
#include <glib-object.h>
#include <stdio.h>
#include <gst/gst.h>
#include <iostream> // test include
#define DUMMY_TEST_CASE
static const gchar* SRC_TYPE = "v4l2src";
static const gchar* SRC_NAME = "video_for_linux_2_source";
static const gchar* H264_ENC_TYPE = "omxh264enc";
static const gchar* H264_ENC_NAME = "H264 Encoder";
static const gchar* RTP_TYPE = "rtph264pay";
static const gchar* RTP_NAME = "RTP payloader for ts";
static const gchar* UDP_SINK_TYPE = "udpsink";
static const gchar* UDP_SINK_NAME = "UDP Sink sender";
static GMainLoop* gLoop;
class TmpEnterExit
{
public:
TmpEnterExit(const char * const apnText) : mpnText(apnText)
{
std::cerr << mpnText << " entering.." << std::endl;
}
~TmpEnterExit()
{
std::cerr << mpnText << " exiting.." << std::endl;
}
private:
const char * const mpnText;
};
static GstPadProbeReturn cbHaveData(
GstPad * ,//apsPad,
GstPadProbeInfo * apsInfo,
gpointer //apsUsrData
)
{
//static bool pbOnce = false;
TmpEnterExit lcTmpEe("cb");
//if(pbOnce)
//{
// return GST_PAD_PROBE_OK;
//}
//
//else
//{
// pbOnce = true;
//}
GstBuffer * lpsBuffer = GST_PAD_PROBE_INFO_BUFFER(apsInfo);
//gpointer lpsBuffer = GST_PAD_PROBE_INFO_DATA(apsInfo);
gpointer lpvState = NULL;
GstMeta * lpsMeta;
if(!lpsBuffer)
{
std::cerr << "buffer does not exist" << std::endl;
std::cerr.flush();
return GST_PAD_PROBE_OK;
}
std::cerr
<< "buffer " << lpsBuffer
<< " about to try to get meta data" << std::endl;
std::cerr.flush();
GQuark lnTypeQname;
GType lnApi;
bool lbFound = false;
while
(
NULL
!= (
lpsMeta = gst_buffer_iterate_meta( lpsBuffer, &lpvState )
)
)
{
lbFound = true;
const GstMetaInfo * lpsMetaInfo = lpsMeta->info;
if( !lpsMetaInfo )
{
std::cerr << "there is no info in the meta..." << std::endl;
std::cerr.flush();
return GST_PAD_PROBE_OK;
}
std::cerr
<< "lpsMetaInfo: '" << lpsMetaInfo
<< "' getting api..." << std::endl;
std::cerr.flush();
lnApi = lpsMetaInfo->api;
std::cerr
<< "lnApi: " << lnApi
<< " getting quark..." << std::endl;
std::cerr.flush();
lnTypeQname = g_type_qname(lnApi);
const gchar * lpnQuarkString = g_quark_to_string(lnTypeQname);
if(!lpnQuarkString)
{
std::cerr
<< "quark: " << lnTypeQname << " has no name" << std::endl;
std::cerr.flush();
return GST_PAD_PROBE_OK;
}
std::cerr
<< "quark: " << lnTypeQname
<< "name: " << lpnQuarkString
<< std::endl;
std::cerr.flush();
}
return GST_PAD_PROBE_OK;
}
struct Pipeline
{
// GstElementFactory* src_factory;
GstElement* backbone;
GstElement* src_element;
GstElement* vid_enc;
GstElement* filter_element;
GstElement* muxer_element;
GstElement* rtp_element;
GstElement* sink_element;
};
int main(int argc, char* argv[])
{
const gchar* nano_str;
guint major, minor, micro, nano;
Pipeline pipeline;
// initialize gstreamer
// using NULL elements instead of command line args
// in examples this is usually: gst_init(&argc, &argv);
gst_init(NULL, NULL);
gLoop = g_main_loop_new(NULL, FALSE);
// get the version we are using and output it
gst_version(&major, &minor, µ, &nano);
if(nano == 1)
{
nano_str = "(CVS)";
}
else if(nano == 2)
{
nano_str = "(Prerelease)";
}
else
{
nano_str = "";
}
printf("This program is linked against GStreamer %d.%d.%d %s\n",
major, minor, micro, nano_str);
// create the pipeline (core bin)
pipeline.backbone = gst_pipeline_new("mpeg-ts pipeline");
//
// Pipeline
// gst-launch-1.0 -v v4l2src device=/dev/video0 ! video/x-raw,width=640,height=480,framerate=30/1 ! omxh264enc ! rtph264pay config-interval=1 pt=96 ! udpsink host=argv[0] port=12345
//
// NOTE: the other side is expected to be:
// udpsrc port=12345 ! application/x-rtp, payload=96"
// ! rtph264depay ! decodebin ! videoconvert ! autovideosink
//
//
// create the source of the pipeline
//
// for now, use a test video source (videotestsrc)
// this portion needs to be replaced by appdata source
pipeline.src_element = gst_element_factory_make(SRC_TYPE, SRC_NAME);
if(!pipeline.src_element)
{
printf("Failed to create element '%s'\n", SRC_NAME);
return -1;
}
else
{
printf("Created element '%s'\n", SRC_NAME);
}
//
// Get the v4l2src pad and update it's caps
//
GstCaps *lpsCaps = gst_caps_new_simple(
"video/x-raw",
"width", G_TYPE_INT, 640,
"height", G_TYPE_INT, 480,
"framerate", GST_TYPE_FRACTION, 30, 1,
NULL );
GstElement * lpsFilter = gst_element_factory_make("capsfilter","filter");
if(!lpsFilter)
{
std::cout << "error in creating caps filter" << std::endl;
return -1;
}
g_object_set(lpsFilter,"caps", lpsCaps, NULL);
gst_caps_unref(lpsCaps);
//
// set up the video encoding
//
pipeline.vid_enc = gst_element_factory_make(
H264_ENC_TYPE, H264_ENC_NAME);
if(!pipeline.vid_enc)
{
printf("Failed to create element '%s'\n", H264_ENC_NAME);
return -1;
}
else
{
printf("Created element '%s'\n", H264_ENC_NAME);
}
//
// set up the RTP
//
pipeline.rtp_element = gst_element_factory_make(RTP_TYPE, RTP_NAME);
if(!pipeline.rtp_element)
{
printf("Failed to create element '%s'\n", RTP_NAME);
return -1;
}
else
{
printf("Created element '%s'\n", RTP_NAME);
}
g_object_set(G_OBJECT(pipeline.rtp_element), "pt", 96, NULL);
g_object_set(G_OBJECT(pipeline.rtp_element), "config-interval", 1, NULL);
//
// Set up the UDP sink aka destination
//
pipeline.sink_element =
gst_element_factory_make(UDP_SINK_TYPE, UDP_SINK_NAME);
if(!pipeline.src_element)
{
printf("Failed to create element '%s'\n", UDP_SINK_NAME);
return -1;
}
else
{
printf("Created element '%s'\n", UDP_SINK_NAME);
}
if(argc < 2)
{
std::cout << "no host given" << std::endl;
return -1;
}
else
{
g_object_set(G_OBJECT(pipeline.sink_element), "host", argv[1], NULL);
}
g_object_set(G_OBJECT(pipeline.sink_element), "port", 12345, NULL);
g_object_set(G_OBJECT(pipeline.sink_element), "sync", TRUE, NULL);
if(!gst_bin_add(GST_BIN(pipeline.backbone), pipeline.src_element) ) {std::cout << "error adding source" << std::endl;}
if(!gst_bin_add(GST_BIN(pipeline.backbone), lpsFilter) ) {std::cout << "error adding source" << std::endl;}
if(!gst_bin_add(GST_BIN(pipeline.backbone), pipeline.vid_enc) ) {std::cout << "error adding encoder" << std::endl;}
if(!gst_bin_add(GST_BIN(pipeline.backbone), pipeline.rtp_element) ) {std::cout << "error adding rtp" << std::endl;}
if(!gst_bin_add(GST_BIN(pipeline.backbone), pipeline.sink_element) ) {std::cout << "error adding sink" << std::endl;}
// try linking the elements
if(!gst_element_link_many(
pipeline.src_element,
lpsFilter,
pipeline.vid_enc,
pipeline.rtp_element,
pipeline.sink_element,
NULL))
{
// TODO cleanup
printf("Pipeline linking failed!");
return -1;
}
else
{
printf("Pipeline link successful");
}
GstPad * tmpPad =
gst_element_get_static_pad(pipeline.rtp_element, "src");
gst_pad_add_probe(
tmpPad,
GST_PAD_PROBE_TYPE_BUFFER,
(GstPadProbeCallback)cbHaveData,
NULL,
NULL);
gst_object_unref(tmpPad);
// Set the pipeline to "playing" state
printf("Setting Pipeline to playing state\n");
gst_element_set_state(pipeline.backbone, GST_STATE_PLAYING);
// Iterate
printf("Running...\n");
g_main_loop_run(gLoop);
// Out of the main loop, clean up nicely
// TODO really need to clean this up properly
// Also need to figure out how/when to terminate the main loop before we clean up
g_print("Returned, stopping playback\n");
gst_element_set_state(pipeline.backbone, GST_STATE_NULL);
g_print("Deleting pipeline\n");
gst_object_unref(GST_OBJECT(pipeline.backbone));
//g_source_remove(bus_watch_id);
g_main_loop_unref(gLoop);
return 0;
}
我找不到一种优雅的方式来检索数据。我只需要查找缓冲区中数据的格式并像这样提取它：
///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
///
/// \brief A callback for the input to the RTP h264 payloader.
///
/// \note There should be multiple RTP outputs and one h264 input per image.
///
/// \details The expected content format is as follows:
/// from https://tools.ietf.org/html/rfc3984#section-5.1
/// 0 1 2 3
/// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/// |V=2|P|X| CC |M| PT | sequence number |
/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/// | timestamp |
/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/// | synchronization source (SSRC) identifier |
/// +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
/// | contributing source (CSRC) identifiers |
/// | .... |
/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
///
///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
static GstPadProbeReturn cbHaveData(
GstPad * ,
GstPadProbeInfo * apsInfo,
gpointer apsUsrData
)
{
//
// Convert the info into something useable...
//
GstBuffer * lpsBuffer = GST_PAD_PROBE_INFO_BUFFER(apsInfo);
if(!lpsBuffer)
{
return GST_PAD_PROBE_OK;
}
GstMapInfo lsMap;
if(!gst_buffer_map(lpsBuffer, &lsMap, GST_MAP_READ))
{
return GST_PAD_PROBE_OK;
}
//
// Get the sequence number from the RTP
//
// get bits 16-31 [2] & [3]
unsigned short lnSeqNum;
int lnSize = 2;
int lnRetVal = gst_buffer_extract(lpsBuffer, 2, (gpointer)&lnSeqNum, lnSize);
if(lnRetVal == lnSize)
{
//
// reverse the bits of the sequence number
//
char * lpnReversedSeqNum = (char*)&lnSeqNum;
unsigned short lnNewSeqNum = 0;
((char*)&lnNewSeqNum)[0] = lpnReversedSeqNum[1];
((char*)&lnNewSeqNum)[1] = lpnReversedSeqNum[0];
printf("sequence number: %d\n", lnNewSeqNum);
}
gst_buffer_unmap(lpsBuffer, &lsMap);
return GST_PAD_PROBE_OK;
}
我仍然愿意接受更好的数据提取方法。
目前，我正在 Linux 环境中使用 udp 将视频从摄像机流式传输到 windows 笔记本电脑。
我正在尝试从 rtph264pay 元素的输出中读取序列号。
我的管道正常工作，并且添加了一个焊盘探针。我不知道如何从数据中读取特定字段，特别是缓冲区中的序列号字段。我该怎么做？
我试图查看缓冲区的元数据中是否有内容。我找不到与缓冲区关联的任何元数据（那是因为 while 循环中没有执行任何内容）。
#include <glib-object.h>
#include <stdio.h>
#include <gst/gst.h>
#include <iostream> // test include
#define DUMMY_TEST_CASE
static const gchar* SRC_TYPE = "v4l2src";
static const gchar* SRC_NAME = "video_for_linux_2_source";
static const gchar* H264_ENC_TYPE = "omxh264enc";
static const gchar* H264_ENC_NAME = "H264 Encoder";
static const gchar* RTP_TYPE = "rtph264pay";
static const gchar* RTP_NAME = "RTP payloader for ts";
static const gchar* UDP_SINK_TYPE = "udpsink";
static const gchar* UDP_SINK_NAME = "UDP Sink sender";
static GMainLoop* gLoop;
class TmpEnterExit
{
public:
TmpEnterExit(const char * const apnText) : mpnText(apnText)
{
std::cerr << mpnText << " entering.." << std::endl;
}
~TmpEnterExit()
{
std::cerr << mpnText << " exiting.." << std::endl;
}
private:
const char * const mpnText;
};
static GstPadProbeReturn cbHaveData(
GstPad * ,//apsPad,
GstPadProbeInfo * apsInfo,
gpointer //apsUsrData
)
{
//static bool pbOnce = false;
TmpEnterExit lcTmpEe("cb");
//if(pbOnce)
//{
// return GST_PAD_PROBE_OK;
//}
//
//else
//{
// pbOnce = true;
//}
GstBuffer * lpsBuffer = GST_PAD_PROBE_INFO_BUFFER(apsInfo);
//gpointer lpsBuffer = GST_PAD_PROBE_INFO_DATA(apsInfo);
gpointer lpvState = NULL;
GstMeta * lpsMeta;
if(!lpsBuffer)
{
std::cerr << "buffer does not exist" << std::endl;
std::cerr.flush();
return GST_PAD_PROBE_OK;
}
std::cerr
<< "buffer " << lpsBuffer
<< " about to try to get meta data" << std::endl;
std::cerr.flush();
GQuark lnTypeQname;
GType lnApi;
bool lbFound = false;
while
(
NULL
!= (
lpsMeta = gst_buffer_iterate_meta( lpsBuffer, &lpvState )
)
)
{
lbFound = true;
const GstMetaInfo * lpsMetaInfo = lpsMeta->info;
if( !lpsMetaInfo )
{
std::cerr << "there is no info in the meta..." << std::endl;
std::cerr.flush();
return GST_PAD_PROBE_OK;
}
std::cerr
<< "lpsMetaInfo: '" << lpsMetaInfo
<< "' getting api..." << std::endl;
std::cerr.flush();
lnApi = lpsMetaInfo->api;
std::cerr
<< "lnApi: " << lnApi
<< " getting quark..." << std::endl;
std::cerr.flush();
lnTypeQname = g_type_qname(lnApi);
const gchar * lpnQuarkString = g_quark_to_string(lnTypeQname);
if(!lpnQuarkString)
{
std::cerr
<< "quark: " << lnTypeQname << " has no name" << std::endl;
std::cerr.flush();
return GST_PAD_PROBE_OK;
}
std::cerr
<< "quark: " << lnTypeQname
<< "name: " << lpnQuarkString
<< std::endl;
std::cerr.flush();
}
return GST_PAD_PROBE_OK;
}
struct Pipeline
{
// GstElementFactory* src_factory;
GstElement* backbone;
GstElement* src_element;
GstElement* vid_enc;
GstElement* filter_element;
GstElement* muxer_element;
GstElement* rtp_element;
GstElement* sink_element;
};
int main(int argc, char* argv[])
{
const gchar* nano_str;
guint major, minor, micro, nano;
Pipeline pipeline;
// initialize gstreamer
// using NULL elements instead of command line args
// in examples this is usually: gst_init(&argc, &argv);
gst_init(NULL, NULL);
gLoop = g_main_loop_new(NULL, FALSE);
// get the version we are using and output it
gst_version(&major, &minor, µ, &nano);
if(nano == 1)
{
nano_str = "(CVS)";
}
else if(nano == 2)
{
nano_str = "(Prerelease)";
}
else
{
nano_str = "";
}
printf("This program is linked against GStreamer %d.%d.%d %s\n",
major, minor, micro, nano_str);
// create the pipeline (core bin)
pipeline.backbone = gst_pipeline_new("mpeg-ts pipeline");
//
// Pipeline
// gst-launch-1.0 -v v4l2src device=/dev/video0 ! video/x-raw,width=640,height=480,framerate=30/1 ! omxh264enc ! rtph264pay config-interval=1 pt=96 ! udpsink host=argv[0] port=12345
//
// NOTE: the other side is expected to be:
// udpsrc port=12345 ! application/x-rtp, payload=96"
// ! rtph264depay ! decodebin ! videoconvert ! autovideosink
//
//
// create the source of the pipeline
//
// for now, use a test video source (videotestsrc)
// this portion needs to be replaced by appdata source
pipeline.src_element = gst_element_factory_make(SRC_TYPE, SRC_NAME);
if(!pipeline.src_element)
{
printf("Failed to create element '%s'\n", SRC_NAME);
return -1;
}
else
{
printf("Created element '%s'\n", SRC_NAME);
}
//
// Get the v4l2src pad and update it's caps
//
GstCaps *lpsCaps = gst_caps_new_simple(
"video/x-raw",
"width", G_TYPE_INT, 640,
"height", G_TYPE_INT, 480,
"framerate", GST_TYPE_FRACTION, 30, 1,
NULL );
GstElement * lpsFilter = gst_element_factory_make("capsfilter","filter");
if(!lpsFilter)
{
std::cout << "error in creating caps filter" << std::endl;
return -1;
}
g_object_set(lpsFilter,"caps", lpsCaps, NULL);
gst_caps_unref(lpsCaps);
//
// set up the video encoding
//
pipeline.vid_enc = gst_element_factory_make(
H264_ENC_TYPE, H264_ENC_NAME);
if(!pipeline.vid_enc)
{
printf("Failed to create element '%s'\n", H264_ENC_NAME);
return -1;
}
else
{
printf("Created element '%s'\n", H264_ENC_NAME);
}
//
// set up the RTP
//
pipeline.rtp_element = gst_element_factory_make(RTP_TYPE, RTP_NAME);
if(!pipeline.rtp_element)
{
printf("Failed to create element '%s'\n", RTP_NAME);
return -1;
}
else
{
printf("Created element '%s'\n", RTP_NAME);
}
g_object_set(G_OBJECT(pipeline.rtp_element), "pt", 96, NULL);
g_object_set(G_OBJECT(pipeline.rtp_element), "config-interval", 1, NULL);
//
// Set up the UDP sink aka destination
//
pipeline.sink_element =
gst_element_factory_make(UDP_SINK_TYPE, UDP_SINK_NAME);
if(!pipeline.src_element)
{
printf("Failed to create element '%s'\n", UDP_SINK_NAME);
return -1;
}
else
{
printf("Created element '%s'\n", UDP_SINK_NAME);
}
if(argc < 2)
{
std::cout << "no host given" << std::endl;
return -1;
}
else
{
g_object_set(G_OBJECT(pipeline.sink_element), "host", argv[1], NULL);
}
g_object_set(G_OBJECT(pipeline.sink_element), "port", 12345, NULL);
g_object_set(G_OBJECT(pipeline.sink_element), "sync", TRUE, NULL);
if(!gst_bin_add(GST_BIN(pipeline.backbone), pipeline.src_element) ) {std::cout << "error adding source" << std::endl;}
if(!gst_bin_add(GST_BIN(pipeline.backbone), lpsFilter) ) {std::cout << "error adding source" << std::endl;}
if(!gst_bin_add(GST_BIN(pipeline.backbone), pipeline.vid_enc) ) {std::cout << "error adding encoder" << std::endl;}
if(!gst_bin_add(GST_BIN(pipeline.backbone), pipeline.rtp_element) ) {std::cout << "error adding rtp" << std::endl;}
if(!gst_bin_add(GST_BIN(pipeline.backbone), pipeline.sink_element) ) {std::cout << "error adding sink" << std::endl;}
// try linking the elements
if(!gst_element_link_many(
pipeline.src_element,
lpsFilter,
pipeline.vid_enc,
pipeline.rtp_element,
pipeline.sink_element,
NULL))
{
// TODO cleanup
printf("Pipeline linking failed!");
return -1;
}
else
{
printf("Pipeline link successful");
}
GstPad * tmpPad =
gst_element_get_static_pad(pipeline.rtp_element, "src");
gst_pad_add_probe(
tmpPad,
GST_PAD_PROBE_TYPE_BUFFER,
(GstPadProbeCallback)cbHaveData,
NULL,
NULL);
gst_object_unref(tmpPad);
// Set the pipeline to "playing" state
printf("Setting Pipeline to playing state\n");
gst_element_set_state(pipeline.backbone, GST_STATE_PLAYING);
// Iterate
printf("Running...\n");
g_main_loop_run(gLoop);
// Out of the main loop, clean up nicely
// TODO really need to clean this up properly
// Also need to figure out how/when to terminate the main loop before we clean up
g_print("Returned, stopping playback\n");
gst_element_set_state(pipeline.backbone, GST_STATE_NULL);
g_print("Deleting pipeline\n");
gst_object_unref(GST_OBJECT(pipeline.backbone));
//g_source_remove(bus_watch_id);
g_main_loop_unref(gLoop);
return 0;
}
我找不到一种优雅的方式来检索数据。我只需要查找缓冲区中数据的格式并像这样提取它：
///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
///
/// \brief A callback for the input to the RTP h264 payloader.
///
/// \note There should be multiple RTP outputs and one h264 input per image.
///
/// \details The expected content format is as follows:
/// from https://tools.ietf.org/html/rfc3984#section-5.1
/// 0 1 2 3
/// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/// |V=2|P|X| CC |M| PT | sequence number |
/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/// | timestamp |
/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/// | synchronization source (SSRC) identifier |
/// +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
/// | contributing source (CSRC) identifiers |
/// | .... |
/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
///
///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
static GstPadProbeReturn cbHaveData(
GstPad * ,
GstPadProbeInfo * apsInfo,
gpointer apsUsrData
)
{
//
// Convert the info into something useable...
//
GstBuffer * lpsBuffer = GST_PAD_PROBE_INFO_BUFFER(apsInfo);
if(!lpsBuffer)
{
return GST_PAD_PROBE_OK;
}
GstMapInfo lsMap;
if(!gst_buffer_map(lpsBuffer, &lsMap, GST_MAP_READ))
{
return GST_PAD_PROBE_OK;
}
//
// Get the sequence number from the RTP
//
// get bits 16-31 [2] & [3]
unsigned short lnSeqNum;
int lnSize = 2;
int lnRetVal = gst_buffer_extract(lpsBuffer, 2, (gpointer)&lnSeqNum, lnSize);
if(lnRetVal == lnSize)
{
//
// reverse the bits of the sequence number
//
char * lpnReversedSeqNum = (char*)&lnSeqNum;
unsigned short lnNewSeqNum = 0;
((char*)&lnNewSeqNum)[0] = lpnReversedSeqNum[1];
((char*)&lnNewSeqNum)[1] = lpnReversedSeqNum[0];
printf("sequence number: %d\n", lnNewSeqNum);
}
gst_buffer_unmap(lpsBuffer, &lsMap);
return GST_PAD_PROBE_OK;
}
我仍然愿意接受更好的数据提取方法。