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add support for feeding gstreamer pipelines into folk image frames
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‎test/gstreamer.tcl‎

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loadVirtualPrograms [list "virtual-programs/gstreamer.folk" "virtual-programs/images.folk"]
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Step
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# namespace eval Pipeline $::makePipeline
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# set pl [Pipeline::create "videotestsrc"]
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# Pipeline::play $pl
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# set img [Pipeline::frame $pl]
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# Pipeline::freeImage $img
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# Pipeline::destroy $pl
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When the gstreamer pipeline "videotestsrc" frame is /frame/ at /ts/ {
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Wish the web server handles route "/gst-image/$" with handler [list apply {{im} {
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set filename "/tmp/web-image-frame.png"
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image saveAsPng $im $filename
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set fsize [file size $filename]
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set fd [open $filename r]
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fconfigure $fd -encoding binary -translation binary
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set body [read $fd $fsize]
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close $fd
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dict create statusAndHeaders "HTTP/1.1 200 OK\nConnection: close\nContent-Type: image/png\nContent-Length: $fsize\n\n" body $body
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}} $frame]
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}
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forever { Step }

‎virtual-programs/gstreamer.folk‎

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set makePipeline {
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rename [c create] cc
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cc cflags {*}[exec pkg-config --cflags --libs gstreamer-1.0]
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cc include <gst/gst.h>
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cc include <assert.h>
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proc defineGObjectType {cc type cast} {
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set cc [uplevel {namespace current}]::$cc
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$cc argtype $type* [format {
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%s* $argname;
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GObject* _$argname;
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sscanf(Tcl_GetString($obj), "(%s) 0x%%p", &_$argname);
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$argname = %s(_$argname);
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} $type $type $cast]
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# Tcl_ObjPrintf doesn't work with %lld/%llx for some reason,
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# so we do it by hand.
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$cc rtype $type* [format {
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$robj = Tcl_ObjPrintf("(%s) 0x%%" PRIxPTR, (uintptr_t) G_OBJECT($rvalue));
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} $type]
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}
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defineImageType cc
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defineGObjectType cc GstElement GST_ELEMENT
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defineGObjectType cc GstBus GST_BUS
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cc struct pipeline_t {
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GstElement* pipeline;
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GstElement* sink;
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GstBus* bus;
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}
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cc struct frame_t {
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bool valid;
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uint64_t timestamp;
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image_t image;
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}
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cc code {
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void log_messages(GstBus* bus) {
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GstMessage* msg;
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GError *err = NULL;
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gchar *dbg_info = NULL;
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while ((msg = gst_bus_pop_filtered(bus, GST_MESSAGE_ERROR | GST_MESSAGE_WARNING))) {
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switch (GST_MESSAGE_TYPE (msg)) {
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case GST_MESSAGE_ERROR: {
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gst_message_parse_error(msg, &err, &dbg_info);
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g_printerr("ERROR from element %s: %s\n", GST_OBJECT_NAME(msg->src), err->message);
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g_printerr("Debugging info: %s\n", (dbg_info) ? dbg_info : "none");
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g_error_free(err);
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g_free(dbg_info);
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break;
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}
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case GST_MESSAGE_WARNING: {
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gst_message_parse_warning(msg, &err, &dbg_info);
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g_printerr("WARNING from element %s: %s\n", GST_OBJECT_NAME(msg->src), err->message);
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g_printerr("Debugging info: %s\n", (dbg_info) ? dbg_info : "none");
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g_error_free(err);
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g_free(dbg_info);
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break;
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}
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default:
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break;
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}
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}
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}
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}
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cc proc destroy {pipeline_t p} void {
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gst_object_unref(p.bus);
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gst_object_unref(p.sink);
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gst_element_set_state(p.pipeline, GST_STATE_NULL);
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gst_object_unref(p.pipeline);
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}
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cc proc create {char* srcdec} pipeline_t {
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GError* err = NULL;
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gst_init(NULL, NULL);
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char buf[512];
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snprintf(buf, sizeof(buf), "%s ! videoconvert ! appsink caps=video/x-raw,format=RGBA name=output drop=true max-buffers=1", srcdec);
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GstElement* pipeline = gst_parse_launch(buf, &err);
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if (err) {
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g_printerr("ERROR launching gst pipeline: %s\n", err->message);
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FOLK_ERROR("Error launching pipeline");
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}
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pipeline_t p;
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p.pipeline = pipeline;
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p.bus = gst_element_get_bus(p.pipeline);
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p.sink = gst_bin_get_by_name(GST_BIN(p.pipeline), "output");
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log_messages(p.bus);
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return p;
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}
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cc proc play {pipeline_t p} void {
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GstState state;
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gst_element_set_state(p.pipeline, GST_STATE_PLAYING);
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gst_element_get_state(p.pipeline, &state, NULL, GST_CLOCK_TIME_NONE);
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log_messages(p.bus);
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if (state != GST_STATE_PLAYING) {
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g_printerr("ERROR launching gst pipeline: pipeline failed to start\n");
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destroy(p);
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FOLK_ERROR("Error starting pipeline playback");
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}
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}
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if {[namespace exists ::Heap]} {
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cc import ::Heap::cc folkHeapAlloc as folkHeapAlloc
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cc import ::Heap::cc folkHeapFree as folkHeapFree
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} else {
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cc code {
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#define folkHeapAlloc malloc
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#define folkHeapFree free
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}
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}
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cc proc frame {pipeline_t p} frame_t {
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frame_t frame;
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GstSample* sample;
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g_signal_emit_by_name(p.sink, "pull-sample", &sample);
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FOLK_CHECK(sample, "pipeline playback stopped");
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GstCaps* caps = gst_sample_get_caps(sample);
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// gst_println("caps are %" GST_PTR_FORMAT, caps);
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GstStructure* s = gst_caps_get_structure(caps, 0);
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FOLK_ENSURE(gst_structure_get_int(s, "width", (gint*)&frame.image.width));
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FOLK_ENSURE(gst_structure_get_int(s, "height", (gint*)&frame.image.height));
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const gchar* format = gst_structure_get_string(s, "format");
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if (g_str_equal(format, "RGB")) {
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frame.image.components = 3;
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} else if (g_str_equal(format, "RGBA")) {
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frame.image.components = 4;
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} else {
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g_printerr("frame: invalid cap format '%s'\n", format);
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FOLK_ERROR("invalid cap format");
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}
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frame.image.bytesPerRow = frame.image.width * frame.image.components;
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GstMapInfo map;
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GstBuffer* buffer = gst_sample_get_buffer(sample);
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gst_buffer_map(buffer, &map, GST_MAP_READ);
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frame.image.data = folkHeapAlloc(map.size);
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memmove(frame.image.data, map.data, map.size);
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frame.timestamp = (uint64_t) GST_BUFFER_DTS(buffer);
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gst_buffer_unmap(buffer, &map);
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gst_sample_unref(sample);
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return frame;
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}
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cc proc freeImage {image_t image} void {
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folkHeapFree(image.data);
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}
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cc compile
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}
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set ::pipelineIndex 0
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When when the gstreamer pipeline /pl/ frame is /frame/ at /ts/ /lambda/ with environment /e/ {
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Start process "gstreamer-[incr ::pipelineIndex]" {
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Wish $::thisProcess shares statements like \
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[list /someone/ claims the gstreamer pipeline /...anything/]
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namespace eval Pipeline $makePipeline
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try {
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set pipe [Pipeline::create $pl]
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Commit { Claim the gstreamer pipeline $pl is starting }
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Pipeline::play $pipe
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Commit { Claim the gstreamer pipeline $pl is playing with time 0 }
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} on error e {
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Commit {
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Claim the gstreamer pipeline $pl is stopped
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Claim the gstreamer pipeline $pl has error $e
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}
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}
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set ::oldFrames [list]
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When the gstreamer pipeline $pl is playing with time /t/ &\
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$::thisProcess has step count /c/ {
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try {
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set frame [Pipeline::frame $pipe]
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dict with frame {
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Commit {
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Claim the gstreamer pipeline $pl is playing with time $timestamp
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Claim the gstreamer pipeline $pl frame is $image at [clock milliseconds]
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}
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lappend ::oldFrames $image
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if {[llength $::oldFrames] >= 10} {
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set ::oldFrames [lassign $::oldFrames oldestFrame]
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Pipeline::freeImage $oldestFrame
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}
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}
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} on error e {
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Commit {
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Claim the gstreamer pipeline $pl is stopped
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Claim the gstreamer pipeline $pl has error $e
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}
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}
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}
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}
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}

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