diff --git a/src/debug.cpp b/src/debug.cpp
index 4b98d3c2d..d33f439af 100644
--- a/src/debug.cpp
+++ b/src/debug.cpp
@@ -87,7 +87,8 @@ static void _dprintf(const char *format, ...)
 #endif                          /* WIN32 */
 }
 
-void log_vprintf(int level, const char *format, va_list ap)
+static void
+log_vprintf(int level, const char *format, va_list ap)
 {
         va_list aq;
 
diff --git a/src/debug.h b/src/debug.h
index 27190f1e6..475283f46 100644
--- a/src/debug.h
+++ b/src/debug.h
@@ -88,7 +88,6 @@ void debug_file_dump(const char *key, void (*serialize)(const void *data, FILE *
 ///#define debug_msg(...) log_msg(LOG_LEVEL_DEBUG, "[pid/%d +%d %s] ", getpid(), __LINE__, __FILE__), log_msg(LOG_LEVEL_DEBUG, __VA_ARGS__)
 #define debug_msg(...) log_msg(LOG_LEVEL_DEBUG, __VA_ARGS__)
 void log_msg(int log_level, const char *format, ...) __attribute__((format (printf, 2, 3)));
-void log_vprintf(int level, const char *format, va_list ap);
 void log_msg_once(int log_level, uint32_t id, const char *msg, ...) __attribute__((format (printf, 3, 4)));
 void log_perror(int log_level, const char *msg);
 #define MSG(l, ...) log_msg(LOG_LEVEL_ ## l, MOD_NAME __VA_ARGS__)
diff --git a/src/libavcodec/lavc_common.c b/src/libavcodec/lavc_common.c
index 18259d771..26bb0d19f 100644
--- a/src/libavcodec/lavc_common.c
+++ b/src/libavcodec/lavc_common.c
@@ -170,21 +170,20 @@ static void av_log_ug_callback(void *avcl, int av_level, const char *fmt, va_lis
         if (av_log_filter(ff_module_name, fmt)) {
                 return;
         }
-        static pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;
-        static _Bool nl_presented = 1;
-        char new_fmt[1024];
-        pthread_mutex_lock(&lock);
-        if (nl_presented) {
+        static _Thread_local char buf[STR_LEN];
+        if (strlen(buf) == 0) {
+                snprintf(buf + strlen(buf), sizeof buf - strlen(buf), "[lavc");
                 if (ff_module_name) {
-                        snprintf(new_fmt, sizeof new_fmt, "[lavc %s @ %p] %s", ff_module_name, avcl, fmt);
-                } else {
-                        snprintf(new_fmt, sizeof new_fmt, "[lavc] %s", fmt);
+                        snprintf(buf + strlen(buf), sizeof buf - strlen(buf),
+                                 " %s @ %p", ff_module_name, avcl);
                 }
-                fmt = new_fmt;
+                snprintf(buf + strlen(buf), sizeof buf - strlen(buf), "] ");
+        }
+        vsnprintf(buf + strlen(buf), sizeof buf - strlen(buf), fmt, vl);
+        if (buf[strlen(buf) - 1] == '\n') {
+                log_msg(level, "%s", buf);
+                buf[0] = '\0';
         }
-        nl_presented = fmt[strlen(fmt) - 1] == '\n';
-        log_vprintf(level, fmt, vl);
-        pthread_mutex_unlock(&lock);
 }
 
 ADD_TO_PARAM("lavcd-log-level",