feat(ffmpeg): logging callback handler

ffmpeg/callback.go

@@ -52,3 +52,8 @@ func goInterrupt(opaque unsafe.Pointer) C.int {
 	}
 	return 0
 }
+
+//export goAVLoggingHandler
+func goAVLoggingHandler(level C.int, cstr *C.char) {
+	log(AVLogLevel(level), C.GoString(cstr))
+}

ffmpeg/ffmpeg.h

@@ -69,4 +69,4 @@ extern int goPacketRead(void *opaque, uint8_t *buf, int buf_size);
 
 extern int64_t goPacketSeek(void *opaque, int64_t seek, int whence);
 
-extern int goInterrupt(void *opaque);
+extern int goInterrupt(void *opaque);

ffmpeg/logging.c

@@ -0,0 +1,12 @@
+#include "logging.h"
+
+void goavLogCallback(void *class_ptr, int level, const char *fmt, va_list vl) {
+    char line[LINE_SZ];
+    int print_prefix = 1;
+    av_log_format_line(class_ptr, level, fmt, vl, line, LINE_SZ, &print_prefix);
+    goAVLoggingHandler(level, line);
+}
+
+void goavLogSetup() {
+    av_log_set_callback(goavLogCallback);
+}

ffmpeg/logging.go

@@ -1,7 +1,9 @@
 package ffmpeg
 
 // #include "ffmpeg.h"
+// #include "logging.h"
 import "C"
+import "sync"
 
 // AVLogLevel defines the ffmpeg threshold for dumping information to stderr.
 type AVLogLevel int
@@ -19,6 +21,12 @@ const (
 	AVLogTrace
 )
 
+var (
+	currentLoggingHandlerFunction = noopLoggingHandler
+	currentLoggingVerbosity       AVLogLevel
+	onceLogging                   sync.Once
+)
+
 func logLevel() AVLogLevel {
 	return AVLogLevel(C.av_log_get_level())
 }
@@ -26,4 +34,25 @@ func logLevel() AVLogLevel {
 // SetFFmpegLogLevel allows you to change the log level from the default (AVLogInfo).
 func SetFFmpegLogLevel(logLevel AVLogLevel) {
 	C.av_log_set_level(C.int(logLevel))
+	currentLoggingVerbosity = logLevel
+}
+
+type LoggingHandlerFunction func(messageLevel AVLogLevel, message string)
+
+func SetLogging(handler LoggingHandlerFunction) {
+	onceLogging.Do(func() {
+		C.goavLogSetup()
+	})
+	if handler != nil {
+		currentLoggingHandlerFunction = handler
+	}
+}
+
+func noopLoggingHandler(_ AVLogLevel, _ string) {
+}
+
+func log(level AVLogLevel, message string) {
+	if level <= currentLoggingVerbosity {
+		currentLoggingHandlerFunction(level, message)
+	}
 }

ffmpeg/logging.h

@@ -0,0 +1,11 @@
+#include <stdarg.h>
+
+#define LINE_SZ 1024
+
+extern void goAVLoggingHandler(int level, char *str);
+extern void av_log_set_callback(void (*callback)(void *, int, const char *, va_list));
+extern void av_log_format_line(void *ptr, int level, const char *fmt, va_list vl, char *line, int line_size, int *print_prefix);
+
+void goavLogCallback(void *class_ptr, int level, const char *fmt, va_list vl);
+
+void goavLogSetup();

processor.go

@@ -29,6 +29,19 @@ func NewProcessor(options ...Option) *Processor {
 }
 
 func (p *Processor) Startup(_ context.Context) error {
+	ffmpeg.SetLogging(func(level ffmpeg.AVLogLevel, message string) {
+		message = strings.TrimSuffix(message, "\n")
+		switch level {
+		case ffmpeg.AVLogTrace, ffmpeg.AVLogDebug, ffmpeg.AVLogVerbose:
+			p.Logger.Debug("ffmpeg", zap.String("msg", message))
+		case ffmpeg.AVLogInfo:
+			p.Logger.Info("ffmpeg", zap.String("msg", message))
+		case ffmpeg.AVLogWarning:
+			p.Logger.Warn("ffmpeg", zap.String("msg", message))
+		case ffmpeg.AVLogError, ffmpeg.AVLogFatal, ffmpeg.AVLogPanic:
+			p.Logger.Error("ffmpeg", zap.String("msg", message))
+		}
+	})
 	if p.Debug {
 		ffmpeg.SetFFmpegLogLevel(ffmpeg.AVLogDebug)
 	} else {