Support recording to MKV

Implement recording to Matroska files.

The format to use is determined by the option -F/--record-format if set,
or by the file extension (".mp4" or ".mkv").

README.md

@@ -162,7 +162,7 @@ It is possible to record the screen while mirroring:
 
 ```bash
 scrcpy --record file.mp4
-scrcpy -r file.mp4
+scrcpy -r file.mkv
 ```
 
 "Skipped frames" are recorded, even if they are not displayed in real time (for

app/src/main.c

@@ -7,11 +7,13 @@
 
 #include "config.h"
 #include "log.h"
+#include "recorder.h"
 
 struct args {
     const char *serial;
     const char *crop;
     const char *record_filename;
+    enum recorder_format record_format;
     SDL_bool fullscreen;
     SDL_bool help;
     SDL_bool version;
@@ -42,6 +44,9 @@ static void usage(const char *arg0) {
         "    -f, --fullscreen\n"
         "        Start in fullscreen.\n"
         "\n"
+        "    -F, --record-format\n"
+        "        Force recording format (either mp4 or mkv).\n"
+        "\n"
         "    -h, --help\n"
         "        Print this help.\n"
         "\n"
@@ -57,6 +62,8 @@ static void usage(const char *arg0) {
         "\n"
         "    -r, --record file.mp4\n"
         "        Record screen to file.\n"
+        "        The format is determined by the -F/--record-format option if\n"
+        "        set, or by the file extension (.mp4 or .mkv).\n"
         "\n"
         "    -s, --serial\n"
         "        The device serial number. Mandatory only if several devices\n"
@@ -208,6 +215,36 @@ static SDL_bool parse_port(char *optarg, Uint16 *port) {
     return SDL_TRUE;
 }
 
+static SDL_bool
+parse_record_format(const char *optarg, enum recorder_format *format) {
+    if (!strcmp(optarg, "mp4")) {
+        *format = RECORDER_FORMAT_MP4;
+        return SDL_TRUE;
+    }
+    if (!strcmp(optarg, "mkv")) {
+        *format = RECORDER_FORMAT_MKV;
+        return SDL_TRUE;
+    }
+    LOGE("Unsupported format: %s (expected mp4 or mkv)", optarg);
+    return SDL_FALSE;
+}
+
+static enum recorder_format
+guess_record_format(const char *filename) {
+    size_t len = strlen(filename);
+    if (len < 4) {
+        return 0;
+    }
+    const char *ext = &filename[len - 4];
+    if (!strcmp(ext, ".mp4")) {
+        return RECORDER_FORMAT_MP4;
+    }
+    if (!strcmp(ext, ".mkv")) {
+        return RECORDER_FORMAT_MKV;
+    }
+    return 0;
+}
+
 static SDL_bool parse_args(struct args *args, int argc, char *argv[]) {
     static const struct option long_options[] = {
         {"always-on-top", no_argument,       NULL, 'T'},
@@ -218,13 +255,14 @@ static SDL_bool parse_args(struct args *args, int argc, char *argv[]) {
         {"max-size",      required_argument, NULL, 'm'},
         {"port",          required_argument, NULL, 'p'},
         {"record",        required_argument, NULL, 'r'},
+        {"record-format", required_argument, NULL, 'f'},
         {"serial",        required_argument, NULL, 's'},
         {"show-touches",  no_argument,       NULL, 't'},
         {"version",       no_argument,       NULL, 'v'},
         {NULL,            0,                 NULL, 0  },
     };
     int c;
-    while ((c = getopt_long(argc, argv, "b:c:fhm:p:r:s:tTv", long_options, NULL)) != -1) {
+    while ((c = getopt_long(argc, argv, "b:c:fF:hm:p:r:s:tTv", long_options, NULL)) != -1) {
         switch (c) {
             case 'b':
                 if (!parse_bit_rate(optarg, &args->bit_rate)) {
@@ -237,6 +275,11 @@ static SDL_bool parse_args(struct args *args, int argc, char *argv[]) {
             case 'f':
                 args->fullscreen = SDL_TRUE;
                 break;
+            case 'F':
+                if (!parse_record_format(optarg, &args->record_format)) {
+                    return SDL_FALSE;
+                }
+                break;
             case 'h':
                 args->help = SDL_TRUE;
                 break;
@@ -276,6 +319,21 @@ static SDL_bool parse_args(struct args *args, int argc, char *argv[]) {
         LOGE("Unexpected additional argument: %s", argv[index]);
         return SDL_FALSE;
     }
+
+    if (args->record_format && !args->record_filename) {
+        LOGE("Record format specified without recording");
+        return SDL_FALSE;
+    }
+
+    if (args->record_filename && !args->record_format) {
+        args->record_format = guess_record_format(args->record_filename);
+        if (!args->record_format) {
+            LOGE("No format specified for \"%s\" (try with -F mkv)",
+                 args->record_filename);
+            return SDL_FALSE;
+        }
+    }
+
     return SDL_TRUE;
 }
 
@@ -290,6 +348,7 @@ int main(int argc, char *argv[]) {
         .serial = NULL,
         .crop = NULL,
         .record_filename = NULL,
+        .record_format = 0,
         .help = SDL_FALSE,
         .version = SDL_FALSE,
         .show_touches = SDL_FALSE,
@@ -329,6 +388,7 @@ int main(int argc, char *argv[]) {
         .crop = args.crop,
         .port = args.port,
         .record_filename = args.record_filename,
+        .record_format = args.record_format,
         .max_size = args.max_size,
         .bit_rate = args.bit_rate,
         .show_touches = args.show_touches,

app/src/recorder.c

@@ -1,6 +1,7 @@
 #include "recorder.h"
 
 #include <libavutil/time.h>
+#include <SDL2/SDL_assert.h>
 
 #include "config.h"
 #include "log.h"
@@ -17,7 +18,7 @@
 
 static const AVRational SCRCPY_TIME_BASE = {1, 1000000}; // timestamps in us
 
-static const AVOutputFormat *find_mp4_muxer(void) {
+static const AVOutputFormat *find_muxer(const char *name) {
 #if LIBAVFORMAT_VERSION_INT >= AV_VERSION_INT(58, 9, 100)
     void *opaque = NULL;
 #endif
@@ -29,11 +30,13 @@ static const AVOutputFormat *find_mp4_muxer(void) {
         oformat = av_oformat_next(oformat);
 #endif
         // until null or with name "mp4"
-    } while (oformat && strcmp(oformat->name, "mp4"));
+    } while (oformat && strcmp(oformat->name, name));
     return oformat;
 }
 
-SDL_bool recorder_init(struct recorder *recorder, const char *filename,
+SDL_bool recorder_init(struct recorder *recorder,
+                       const char *filename,
+                       enum recorder_format format,
                        struct size declared_frame_size) {
     recorder->filename = SDL_strdup(filename);
     if (!recorder->filename) {
@@ -41,6 +44,7 @@ SDL_bool recorder_init(struct recorder *recorder, const char *filename,
         return SDL_FALSE;
     }
 
+    recorder->format = format;
     recorder->declared_frame_size = declared_frame_size;
     recorder->header_written = SDL_FALSE;
 
@@ -51,10 +55,21 @@ void recorder_destroy(struct recorder *recorder) {
     SDL_free(recorder->filename);
 }
 
+static const char *
+recorder_get_format_name(enum recorder_format format) {
+    switch (format) {
+        case RECORDER_FORMAT_MP4: return "mp4";
+        case RECORDER_FORMAT_MKV: return "matroska";
+        default: return NULL;
+    }
+}
+
 SDL_bool recorder_open(struct recorder *recorder, AVCodec *input_codec) {
-    const AVOutputFormat *mp4 = find_mp4_muxer();
+    const char *format_name = recorder_get_format_name(recorder->format);
-    if (!mp4) {
+    SDL_assert(format_name);
-        LOGE("Could not find mp4 muxer");
+    const AVOutputFormat *format = find_muxer(format_name);
+    if (!format) {
+        LOGE("Could not find muxer");
         return SDL_FALSE;
     }
 
@@ -68,7 +83,7 @@ SDL_bool recorder_open(struct recorder *recorder, AVCodec *input_codec) {
     // returns (on purpose) a pointer-to-const, but AVFormatContext.oformat
     // still expects a pointer-to-non-const (it has not be updated accordingly)
     // <https://github.com/FFmpeg/FFmpeg/commit/0694d8702421e7aff1340038559c438b61bb30dd>
-    recorder->ctx->oformat = (AVOutputFormat *) mp4;
+    recorder->ctx->oformat = (AVOutputFormat *) format;
 
     AVStream *ostream = avformat_new_stream(recorder->ctx, input_codec);
     if (!ostream) {

app/src/recorder.h

@@ -6,15 +6,24 @@
 
 #include "common.h"
 
+enum recorder_format {
+    RECORDER_FORMAT_MP4 = 1,
+    RECORDER_FORMAT_MKV,
+};
+
 struct recorder {
     char *filename;
+    enum recorder_format format;
     AVFormatContext *ctx;
     struct size declared_frame_size;
     SDL_bool header_written;
 };
 
-SDL_bool recorder_init(struct recorder *recoder, const char *filename,
+SDL_bool recorder_init(struct recorder *recoder,
+                       const char *filename,
+                       enum recorder_format format,
                        struct size declared_frame_size);
+
 void recorder_destroy(struct recorder *recorder);
 
 SDL_bool recorder_open(struct recorder *recorder, AVCodec *input_codec);

app/src/scrcpy.c

@@ -229,7 +229,10 @@ SDL_bool scrcpy(const struct scrcpy_options *options) {
 
     struct recorder *rec = NULL;
     if (options->record_filename) {
-        if (!recorder_init(&recorder, options->record_filename, frame_size)) {
+        if (!recorder_init(&recorder,
+                           options->record_filename,
+                           options->record_format,
+                           frame_size)) {
             ret = SDL_FALSE;
             server_stop(&server);
             goto finally_destroy_file_handler;

app/src/scrcpy.h

@@ -2,11 +2,13 @@
 #define SCRCPY_H
 
 #include <SDL2/SDL_stdinc.h>
+#include <recorder.h>
 
 struct scrcpy_options {
     const char *serial;
     const char *crop;
     const char *record_filename;
+    enum recorder_format record_format;
     Uint16 port;
     Uint16 max_size;
     Uint32 bit_rate;