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/*
* Copyright (C) 2023 Igalia S.L
* Copyright (C) 2023 Metrological Group B.V.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "config.h"
#include "GStreamerSinksWorkarounds.h"
#if USE(GSTREAMER)
#include "GStreamerCommon.h"
#include <gst/base/gstbasesink.h>
#include <gst/gst.h>
#include <gst/pbutils/gstpluginsbaseversion.h>
#include <mutex>
#include <wtf/PrintStream.h>
#include <wtf/glib/GRefPtr.h>
#include <wtf/glib/WTFGType.h>
GST_DEBUG_CATEGORY(webkit_workarounds_debug);
#define GST_CAT_DEFAULT webkit_workarounds_debug
namespace WebCore {
enum class WorkaroundMode {
UseIfNeeded, // default
ForceEnable,
ForceDisable,
};
// These environment variables can be used to enable or disable workarounds at build time, if desired.
// This is useful when running patched GStreamer versions, for instance.
#ifndef WEBKIT_GST_WORKAROUND_APP_SINK_FLUSH_CAPS_DEFAULT_MODE
#define WEBKIT_GST_WORKAROUND_APP_SINK_FLUSH_CAPS_DEFAULT_MODE "UseIfNeeded"
#endif
#ifndef WEBKIT_GST_WORKAROUND_BASE_SINK_POSITION_FLUSH_DEFAULT_MODE
#define WEBKIT_GST_WORKAROUND_BASE_SINK_POSITION_FLUSH_DEFAULT_MODE "UseIfNeeded"
#endif
static WorkaroundMode getWorkAroundModeFromEnvironment(const char* environmentVariableName, const char* defaultValue)
{
const char* textValue = getenv(environmentVariableName);
if (!textValue)
textValue = defaultValue;
if (!g_ascii_strcasecmp(textValue, "UseIfNeeded"))
return WorkaroundMode::UseIfNeeded;
if (!g_ascii_strcasecmp(textValue, "ForceEnable"))
return WorkaroundMode::ForceEnable;
if (!g_ascii_strcasecmp(textValue, "ForceDisable"))
return WorkaroundMode::ForceDisable;
GST_ERROR("Invalid value for %s: '%s'. Accepted values are 'UseIfNeeded', 'ForceEnable' and 'ForceDisable'. Defaulting to `UseIfNeeded`...", environmentVariableName, textValue);
return WorkaroundMode::UseIfNeeded;
}
// Workaround for: https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/3471 basesink: Support position queries after non-resetting flushes.
// Fix merged in 1.23, shipped in GStreamer 1.24.0.
class BaseSinkPositionFlushWorkaroundProbe {
public:
static bool isNeeded()
{
static std::once_flag onceFlag;
std::call_once(onceFlag, initializeIsNeeded);
return s_isNeeded;
}
static void installIfNeeded(GstBaseSink* basesink)
{
ASSERT(GST_IS_BASE_SINK(basesink));
if (!isNeeded())
return;
GRefPtr<GstPad> pad = adoptGRef(gst_element_get_static_pad(GST_ELEMENT(basesink), "sink"));
GST_DEBUG_OBJECT(pad.get(), "Installing BaseSinkPositionFlushWorkaroundProbe.");
gst_pad_add_probe(pad.get(), static_cast<GstPadProbeType>(GST_PAD_PROBE_TYPE_EVENT_FLUSH),
probe, newUserData(), deleteUserData);
}
private:
static bool s_isNeeded;
bool m_isHandlingFlushStop { false };
static bool checkIsNeeded()
{
#ifndef GST_DISABLE_GST_DEBUG
GUniquePtr<char> versionString(gst_version_string());
GST_DEBUG("BaseSinkPositionFlushWorkaroundProbe: running %s, the bug was fixed in 1.24.", versionString.get());
#endif
WorkaroundMode mode = getWorkAroundModeFromEnvironment("WEBKIT_GST_WORKAROUND_BASE_SINK_POSITION_FLUSH", WEBKIT_GST_WORKAROUND_BASE_SINK_POSITION_FLUSH_DEFAULT_MODE);
if (mode == WorkaroundMode::ForceEnable) {
GST_DEBUG("BaseSinkPositionFlushWorkaroundProbe: forcing workaround to be enabled.");
return true;
}
if (mode == WorkaroundMode::ForceDisable) {
GST_DEBUG("BaseSinkPositionFlushWorkaroundProbe: forcing workaround to be disabled.");
return false;
}
return !webkitGstCheckVersion(1, 24, 0);
}
static void initializeIsNeeded()
{
s_isNeeded = checkIsNeeded();
GST_DEBUG("BaseSinkPositionFlushWorkaroundProbe is%s needed in this system.", s_isNeeded ? "" : " NOT");
}
static bool flushIsNonResetting(GstEvent* event)
{
gboolean resetTime = TRUE;
gst_event_parse_flush_stop(event, &resetTime);
return !resetTime;
}
static GstPadProbeReturn probe(GstPad* pad, GstPadProbeInfo* info, void* userData)
{
auto* self = static_cast<BaseSinkPositionFlushWorkaroundProbe*>(userData);
GRefPtr<GstBaseSink> basesink = adoptGRef(GST_BASE_SINK(gst_pad_get_parent(pad)));
GST_TRACE_OBJECT(pad, "m_isHandlingFlushStop: %s, pad is flushing: %s, received: %" GST_PTR_FORMAT, boolForPrinting(self->m_isHandlingFlushStop), boolForPrinting(GST_PAD_IS_FLUSHING(pad)), info->data);
if (!self->m_isHandlingFlushStop && (info->type & GST_PAD_PROBE_TYPE_EVENT_FLUSH) && GST_EVENT_TYPE(GST_PAD_PROBE_INFO_EVENT(info)) == GST_EVENT_FLUSH_STOP
&& flushIsNonResetting(GST_PAD_PROBE_INFO_EVENT(info)) && basesink->segment.format != GST_FORMAT_UNDEFINED)
{
GST_DEBUG_OBJECT(pad, "Received non-resetting FLUSH_STOP while we have a valid segment... propagating the FLUSH_STOP.");
self->m_isHandlingFlushStop = true;
gst_pad_send_event(pad, GST_EVENT(info->data));
self->m_isHandlingFlushStop = false;
// For non-resetting FLUSH_STOP events basesink preserves the segment but still sets have_newsegment to FALSE.
// Until the fix was introduced, this makes gst_base_sink_get_position() fail.
// The workaround consists on setting have_newsegment to TRUE in that case after the FLUSH_STOP is handled
// internally by basesink.
//
// This is a reasonably safe workaround, as the only other place where have_newsegment is read is in a warning
// message in gst_base_sink_chain_unlocked() for when a buffer is pushed without a segment, something that
// shouldn't happen in the first place.
GST_DEBUG_OBJECT(pad, "Non-resetting FLUSH_STOP has been handled by this element and its downstream. Now force position queries to work by setting basesink->have_newsegment to TRUE.");
basesink->have_newsegment = TRUE;
return GST_PAD_PROBE_HANDLED;
}
return GST_PAD_PROBE_OK;
}
static void* newUserData() { return new BaseSinkPositionFlushWorkaroundProbe; }
static void deleteUserData(void* self) { delete static_cast<BaseSinkPositionFlushWorkaroundProbe*>(self); }
};
bool BaseSinkPositionFlushWorkaroundProbe::s_isNeeded;
// Workaround for https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/2413 appsink: Fix race condition on caps handling
// Fix landed upstream in 1.20.3, 1.21.1, 1.22.0.
class AppSinkFlushCapsWorkaroundProbe {
public:
static bool isNeeded()
{
static std::once_flag onceFlag;
std::call_once(onceFlag, initializeIsNeeded);
return s_isNeeded;
}
static void installIfNeeded(GstAppSink* appsink)
{
ASSERT(GST_IS_APP_SINK(appsink));
if (!isNeeded())
return;
GRefPtr<GstPad> pad = adoptGRef(gst_element_get_static_pad(GST_ELEMENT(appsink), "sink"));
GST_DEBUG_OBJECT(pad.get(), "Installing AppSinkFlushCapsWorkaroundProbe.");
gst_pad_add_probe(pad.get(), static_cast<GstPadProbeType>(GST_PAD_PROBE_TYPE_BUFFER | GST_PAD_PROBE_TYPE_EVENT_FLUSH | GST_PAD_PROBE_TYPE_EVENT_DOWNSTREAM),
probe, newUserData(), deleteUserData);
}
private:
static bool s_isNeeded;
// Must only be read and written with the pad lock.
bool m_needsResendCaps { false };
static bool checkIsNeeded()
{
// Instantiate an appsink once to force gst-plugins-base to load.
GRefPtr<GstElementFactory> factoryAppSink = adoptGRef(gst_element_factory_find("appsink"));
if (!factoryAppSink) {
WTFLogAlways("GStreamer element appsink not found. Please install it.");
return false;
}
#ifndef GST_DISABLE_GST_DEBUG
GUniquePtr<char> version(gst_plugins_base_version_string());
GST_DEBUG("AppSinkFlushCapsWorkaroundProbe: gst-plugins-base version is %s, bug was fixed in 1.21.1 and backported to 1.20.3.", version.get());
#endif
WorkaroundMode mode = getWorkAroundModeFromEnvironment("WEBKIT_GST_WORKAROUND_APP_SINK_FLUSH_CAPS", WEBKIT_GST_WORKAROUND_APP_SINK_FLUSH_CAPS_DEFAULT_MODE);
if (mode == WorkaroundMode::ForceEnable) {
GST_DEBUG("AppSinkFlushCapsWorkaroundProbe: forcing workaround to be enabled.");
return true;
}
if (mode == WorkaroundMode::ForceDisable) {
GST_DEBUG("AppSinkFlushCapsWorkaroundProbe: forcing workaround to be disabled.");
return false;
}
guint major, minor, micro;
gst_plugins_base_version(&major, &minor, µ, nullptr);
if (major < 1)
return true;
if (major > 1)
return false;
if (minor < 20)
return true;
if (minor >= 22)
return false;
if (minor == 21)
return micro < 1; // Fix landed in 1.21.1 https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/2413
ASSERT(minor == 20);
return micro < 3; // Fix was backported to 1.20.3 https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/2442
}
static void initializeIsNeeded()
{
s_isNeeded = checkIsNeeded();
GST_DEBUG("AppSinkFlushCapsWorkaroundProbe is%s needed in this system.", s_isNeeded ? "" : " NOT");
}
static GstPadProbeReturn probe(GstPad* pad, GstPadProbeInfo* info, void* userData)
{
auto* self = static_cast<AppSinkFlushCapsWorkaroundProbe*>(userData);
// Changes to the flushing flag of a pad only occur while the pad lock is held.
// By holding it, we can reliably prevent the flushing flag from changing during the execution of our code.
// The pad lock also ensures there are no data races over `priv->needsResendCaps`.
GstObjectLocker padLocker(pad);
bool willResendCaps = false;
if ((info->type & GST_PAD_PROBE_TYPE_EVENT_FLUSH) && GST_EVENT_TYPE(info->data) == GST_EVENT_FLUSH_STOP) {
GST_TRACE_OBJECT(pad, "Flush event received, setting needsResendCaps = true");
self->m_needsResendCaps = true;
} else if (!GST_PAD_IS_FLUSHING(pad) && (info->type & GST_PAD_PROBE_TYPE_EVENT_DOWNSTREAM) && GST_EVENT_TYPE(info->data) == GST_EVENT_CAPS) {
GST_TRACE_OBJECT(pad, "Caps event received, setting needsResendCaps = false");
self->m_needsResendCaps = false;
} else if (!GST_PAD_IS_FLUSHING(pad) && (info->type & GST_PAD_PROBE_TYPE_BUFFER) && self->m_needsResendCaps) {
GST_DEBUG_OBJECT(pad, "Buffer received, but first need to resend pad caps to workaround bug. Will resend caps.");
willResendCaps = true;
}
padLocker.unlockEarly();
if (willResendCaps) {
GRefPtr<GstCaps> caps = adoptGRef(gst_pad_get_current_caps(pad));
GST_DEBUG_OBJECT(pad, "Sending stored pad caps to appsink: %" GST_PTR_FORMAT, caps.get());
// This will cause a recursive call to appsinkWorkaroundProbe() which will also set `needsResendCaps` to false.
[[maybe_unused]] bool wereCapsSent = gst_pad_send_event(pad, gst_event_new_caps(caps.get()));
GST_DEBUG_OBJECT(pad, "wereCapsSent = %s. Returning from the probe so that the buffer is sent: %" GST_PTR_FORMAT, boolForPrinting(wereCapsSent), info->data);
}
return GST_PAD_PROBE_OK;
}
static void* newUserData() { return new AppSinkFlushCapsWorkaroundProbe; }
static void deleteUserData(void* self) { delete static_cast<AppSinkFlushCapsWorkaroundProbe*>(self); }
};
bool AppSinkFlushCapsWorkaroundProbe::s_isNeeded;
static void registerAppsinkWithWorkaroundsIfNeededCallOnce()
{
// If any workarounds are needed in this system, override GStreamer appsink for a version containing any needed workarounds.
GST_DEBUG_CATEGORY_INIT(webkit_workarounds_debug, "webkitworkarounds", 0, "WebKit GStreamer Workarounds");
GST_DEBUG("Checking for potentially needed GStreamer workarounds...");
bool doesNeedWorkarounds = BaseSinkPositionFlushWorkaroundProbe::isNeeded() || AppSinkFlushCapsWorkaroundProbe::isNeeded();
GST_DEBUG("WebKitAppsinkWithWorkarounds WILL%s be registered.", doesNeedWorkarounds ? "" : " NOT");
if (!doesNeedWorkarounds)
return;
// Here is some quirkiness: We need to load both appsrc and appsink, as both will cause plugin_init() to
// be called, which will register both elements.
// If we don't ensure the appsrc factory has been loaded before registering our appsink override, appsink
// will be re-registered by the "app" plugin next time an appsrc is requested, overwriting our workaround.
GRefPtr<GstElement>(gst_element_factory_make("appsink", "preload-dummy-appsink"));
GRefPtr<GstElement>(gst_element_factory_make("appsrc", "preload-dummy-appsrc"));
gst_element_register(nullptr, "appsink", GST_RANK_PRIMARY + 1000, WEBKIT_TYPE_APP_SINK_WITH_WORKAROUNDS);
}
void registerAppsinkWithWorkaroundsIfNeeded()
{
static std::once_flag onceFlag;
std::call_once(onceFlag, registerAppsinkWithWorkaroundsIfNeededCallOnce);
}
void installBaseSinkPositionFlushWorkaroundIfNeeded(GstBaseSink* basesink)
{
return BaseSinkPositionFlushWorkaroundProbe::installIfNeeded(basesink);
}
} // namespace WebCore
struct WebKitAppSinkWithWorkaroundsPrivate {
};
WEBKIT_DEFINE_TYPE(WebKitAppSinkWithWorkarounds, webkit_app_sink_with_workarounds, GST_TYPE_APP_SINK);
static void webkitAppSinkWithWorkAroundsConstructed(GObject* object)
{
G_OBJECT_CLASS(webkit_app_sink_with_workarounds_parent_class)->constructed(object);
GST_DEBUG_OBJECT(object, "WebKitAppSinkWithWorkarounds instantiated.");
WebCore::AppSinkFlushCapsWorkaroundProbe::installIfNeeded(GST_APP_SINK(object));
WebCore::installBaseSinkPositionFlushWorkaroundIfNeeded(GST_BASE_SINK(object));
}
static void webkit_app_sink_with_workarounds_class_init(WebKitAppSinkWithWorkaroundsClass* klass)
{
auto* gobjectClass = G_OBJECT_CLASS(klass);
gobjectClass->constructed = webkitAppSinkWithWorkAroundsConstructed;
}
#undef GST_CAT_DEFAULT
#endif // USE(GSTREAMER)
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