register our own log handler for ffmpeg using QLoggingCategory

CMakeLists.txt

@@ -3,7 +3,7 @@ project(ffmpegthumbs)
 cmake_minimum_required(VERSION 2.8.12 FATAL_ERROR)
 set(QT_MIN_VERSION "5.2.0")
 
-find_package(ECM 1.0.0 REQUIRED NO_MODULE)
+find_package(ECM 5.14.0 REQUIRED NO_MODULE)
 set(CMAKE_MODULE_PATH ${ECM_MODULE_PATH} ${ECM_KDE_MODULE_DIR} ${CMAKE_CURRENT_SOURCE_DIR}/cmake)
 
 include(FeatureSummary)
@@ -11,6 +11,7 @@ include(WriteBasicConfigVersionFile)
 include(KDEInstallDirs)
 include(KDECMakeSettings)
 include(KDECompilerSettings NO_POLICY_SCOPE)
+include(ECMQtDeclareLoggingCategory)
 
 find_package(Qt5 ${QT_MIN_VERSION} CONFIG REQUIRED COMPONENTS Core Gui)
 find_package(KF5 REQUIRED COMPONENTS KIO I18n Config)
@@ -37,6 +38,8 @@ set( ffmpegthumbs_PART_SRCS
   ffmpegthumbnailer/videothumbnailer.cpp
 )
 
+ecm_qt_declare_logging_category(ffmpegthumbs_PART_SRCS HEADER ffmpegthumbs_debug.h IDENTIFIER ffmpegthumbs_LOG CATEGORY_NAME org.kde.kdemultimedia.ffmpegthumbs DEFAULT_SEVERITY Critical)
+
 kconfig_add_kcfg_files(ffmpegthumbs_PART_SRCS ffmpegthumbnailersettings5.kcfgc)
 add_library(ffmpegthumbs MODULE ${ffmpegthumbs_PART_SRCS})
 

ffmpegthumbnailer.cpp

@@ -17,6 +17,7 @@
 
 #include "ffmpegthumbnailer.h"
 #include "ffmpegthumbnailersettings5.h"
+#include "ffmpegthumbs_debug.h"
 
 #include <taglib/mp4file.h>
 
@@ -24,10 +25,52 @@
 #include <QCheckBox>
 #include <KLocalizedString>
 
+extern "C" {
+#include <libavutil/log.h>
+}
+
+namespace {
+struct FFmpegLogHandler {
+    static void handleMessage(void *ptr, int level, const char *fmt, va_list vargs) {
+        Q_UNUSED(ptr);
+
+        const QString message = QString::vasprintf(fmt, vargs);
+
+        switch(level) {
+        case AV_LOG_PANIC: // ffmpeg will crash now
+            qCCritical(ffmpegthumbs_LOG) << message;
+            break;
+        case AV_LOG_FATAL: // fatal as in can't decode, not crash
+        case AV_LOG_ERROR:
+        case AV_LOG_WARNING:
+            qCWarning(ffmpegthumbs_LOG) << message;
+            break;
+        case AV_LOG_INFO:
+            qCInfo(ffmpegthumbs_LOG) << message;
+            break;
+        case AV_LOG_VERBOSE:
+        case AV_LOG_DEBUG:
+            qCDebug(ffmpegthumbs_LOG) << message;
+            break;
+        default:
+            qCWarning(ffmpegthumbs_LOG) << "unhandled log level" << level << message;
+            break;
+        }
+    }
+
+    FFmpegLogHandler() {
+        av_log_set_callback(&FFmpegLogHandler::handleMessage);
+    }
+};
+} //namespace
+
 extern "C"
 {
     Q_DECL_EXPORT ThumbCreator *new_creator()
     {
+        // This is a threadsafe way to ensure that we only register it once
+        static FFmpegLogHandler handler;
+
         return new FFMpegThumbnailer();
     }
 }

tests/CMakeLists.txt

@@ -15,6 +15,7 @@ set(ffmpegthumbtest_SRCS ffmpegthumbtest.cpp
 	${CMAKE_CURRENT_SOURCE_DIR}/../ffmpegthumbnailer/imagewriter.cpp
 	${CMAKE_CURRENT_SOURCE_DIR}/../ffmpegthumbnailer/videothumbnailer.cpp
 )
+ecm_qt_declare_logging_category(ffmpegthumbtest_SRCS HEADER ffmpegthumbs_debug.h IDENTIFIER ffmpegthumbs_LOG CATEGORY_NAME org.kde.kdemultimedia.ffmpegthumbs DEFAULT_SEVERITY Critical)
 
 kconfig_add_kcfg_files(ffmpegthumbtest_SRCS ${CMAKE_CURRENT_SOURCE_DIR}/../ffmpegthumbnailersettings5.kcfgc)