Accept .m4a and .mka

These are just aliases for mp4 and mkv when there is no video stream.

PR #3978 <https://github.com/Genymobile/scrcpy/pull/3978>

app/src/cli.c

@@ -1487,6 +1487,12 @@ get_record_format(const char *name) {
     if (!strcmp(name, "mkv")) {
         return SC_RECORD_FORMAT_MKV;
     }
+    if (!strcmp(name, "m4a")) {
+        return SC_RECORD_FORMAT_M4A;
+    }
+    if (!strcmp(name, "mka")) {
+        return SC_RECORD_FORMAT_MKA;
+    }
     return 0;
 }
 
@@ -1974,6 +1980,12 @@ parse_args_with_getopt(struct scrcpy_cli_args *args, int argc, char *argv[],
             LOGW("Recording does not support RAW audio codec");
             return false;
         }
+
+        if (opts->video
+                && sc_record_format_is_audio_only(opts->record_format)) {
+            LOGE("Audio container does not support video stream");
+            return false;
+        }
     }
 
     if (opts->audio_codec == SC_CODEC_RAW) {

app/src/options.h

@@ -21,8 +21,16 @@ enum sc_record_format {
     SC_RECORD_FORMAT_AUTO,
     SC_RECORD_FORMAT_MP4,
     SC_RECORD_FORMAT_MKV,
+    SC_RECORD_FORMAT_M4A,
+    SC_RECORD_FORMAT_MKA,
 };
 
+static inline bool
+sc_record_format_is_audio_only(enum sc_record_format fmt) {
+    return fmt == SC_RECORD_FORMAT_M4A
+        || fmt == SC_RECORD_FORMAT_MKA;
+}
+
 enum sc_codec {
     SC_CODEC_H264,
     SC_CODEC_H265,

app/src/recorder.c

@@ -60,9 +60,14 @@ sc_recorder_queue_clear(struct sc_recorder_queue *queue) {
 static const char *
 sc_recorder_get_format_name(enum sc_record_format format) {
     switch (format) {
-        case SC_RECORD_FORMAT_MP4: return "mp4";
-        case SC_RECORD_FORMAT_MKV: return "matroska";
-        default: return NULL;
+        case SC_RECORD_FORMAT_MP4:
+        case SC_RECORD_FORMAT_M4A:
+            return "mp4";
+        case SC_RECORD_FORMAT_MKV:
+        case SC_RECORD_FORMAT_MKA:
+            return "matroska";
+        default:
+            return NULL;
     }
 }