Add option to select video codec

Introduce the selection mechanism. Alternative codecs will be added in
further commits.

PR #3713 <https://github.com/Genymobile/scrcpy/pull/3713>

app/scrcpy.1

@@ -25,6 +25,10 @@ Encode the video at the given bit\-rate, expressed in bits/s. Unit suffixes are
 
 Default is 8000000.
 
+.TP
+.BI "\-\-codec " name
+Select a video codec (h264).
+
 .TP
 .BI "\-\-codec\-options " key\fR[:\fItype\fR]=\fIvalue\fR[,...]
 Set a list of comma-separated key:type=value options for the device encoder.

app/src/cli.c

@@ -57,6 +57,7 @@
 #define OPT_NO_CLEANUP             1037
 #define OPT_PRINT_FPS              1038
 #define OPT_NO_POWER_ON            1039
+#define OPT_CODEC                  1040
 
 struct sc_option {
     char shortopt;
@@ -105,6 +106,12 @@ static const struct sc_option options[] = {
                 "Unit suffixes are supported: 'K' (x1000) and 'M' (x1000000).\n"
                 "Default is " STR(DEFAULT_BIT_RATE) ".",
     },
+    {
+        .longopt_id = OPT_CODEC,
+        .longopt = "codec",
+        .argdesc = "name",
+        .text = "Select a video codec (h264).",
+    },
     {
         .longopt_id = OPT_CODEC_OPTIONS,
         .longopt = "codec-options",
@@ -1377,6 +1384,16 @@ guess_record_format(const char *filename) {
     return 0;
 }
 
+static bool
+parse_codec(const char *optarg, enum sc_codec *codec) {
+    if (!strcmp(optarg, "h264")) {
+        *codec = SC_CODEC_H264;
+        return true;
+    }
+    LOGE("Unsupported codec: %s (expected h264)", optarg);
+    return false;
+}
+
 static bool
 parse_args_with_getopt(struct scrcpy_cli_args *args, int argc, char *argv[],
                        const char *optstring, const struct option *longopts) {
@@ -1610,6 +1627,11 @@ parse_args_with_getopt(struct scrcpy_cli_args *args, int argc, char *argv[],
             case OPT_PRINT_FPS:
                 opts->start_fps_counter = true;
                 break;
+            case OPT_CODEC:
+                if (!parse_codec(optarg, &opts->codec)) {
+                    return false;
+                }
+                break;
             case OPT_OTG:
 #ifdef HAVE_USB
                 opts->otg = true;

app/src/demuxer.c

@@ -17,6 +17,25 @@
 
 #define SC_PACKET_PTS_MASK (SC_PACKET_FLAG_KEY_FRAME - 1)
 
+static enum AVCodecID
+sc_demuxer_recv_codec_id(struct sc_demuxer *demuxer) {
+    uint8_t data[4];
+    ssize_t r = net_recv_all(demuxer->socket, data, 4);
+    if (r < 4) {
+        return false;
+    }
+
+#define SC_CODEC_ID_H264 UINT32_C(0x68323634) // "h264" in ASCII
+    uint32_t codec_id = sc_read32be(data);
+    switch (codec_id) {
+        case SC_CODEC_ID_H264:
+            return AV_CODEC_ID_H264;
+        default:
+            LOGE("Unknown codec id 0x%08" PRIx32, codec_id);
+            return AV_CODEC_ID_NONE;
+    }
+}
+
 static bool
 sc_demuxer_recv_packet(struct sc_demuxer *demuxer, AVPacket *packet) {
     // The video stream contains raw packets, without time information. When we
@@ -171,7 +190,13 @@ static int
 run_demuxer(void *data) {
     struct sc_demuxer *demuxer = data;
 
-    const AVCodec *codec = avcodec_find_decoder(AV_CODEC_ID_H264);
+    enum AVCodecID codec_id = sc_demuxer_recv_codec_id(demuxer);
+    if (codec_id == AV_CODEC_ID_NONE) {
+        // Error already logged
+        goto end;
+    }
+
+    const AVCodec *codec = avcodec_find_decoder(codec_id);
     if (!codec) {
         LOGE("H.264 decoder not found");
         goto end;
@@ -188,7 +213,7 @@ run_demuxer(void *data) {
         goto finally_free_codec_ctx;
     }
 
-    demuxer->parser = av_parser_init(AV_CODEC_ID_H264);
+    demuxer->parser = av_parser_init(codec_id);
     if (!demuxer->parser) {
         LOGE("Could not initialize parser");
         goto finally_close_sinks;

app/src/options.c

@@ -13,6 +13,7 @@ const struct scrcpy_options scrcpy_options_default = {
     .v4l2_device = NULL,
 #endif
     .log_level = SC_LOG_LEVEL_INFO,
+    .codec = SC_CODEC_H264,
     .record_format = SC_RECORD_FORMAT_AUTO,
     .keyboard_input_mode = SC_KEYBOARD_INPUT_MODE_INJECT,
     .port_range = {

app/src/options.h

@@ -23,6 +23,10 @@ enum sc_record_format {
     SC_RECORD_FORMAT_MKV,
 };
 
+enum sc_codec {
+    SC_CODEC_H264,
+};
+
 enum sc_lock_video_orientation {
     SC_LOCK_VIDEO_ORIENTATION_UNLOCKED = -1,
     // lock the current orientation when scrcpy starts
@@ -93,6 +97,7 @@ struct scrcpy_options {
     const char *v4l2_device;
 #endif
     enum sc_log_level log_level;
+    enum sc_codec codec;
     enum sc_record_format record_format;
     enum sc_keyboard_input_mode keyboard_input_mode;
     enum sc_mouse_input_mode mouse_input_mode;

app/src/scrcpy.c

@@ -315,6 +315,7 @@ scrcpy(struct scrcpy_options *options) {
         .select_usb = options->select_usb,
         .select_tcpip = options->select_tcpip,
         .log_level = options->log_level,
+        .codec = options->codec,
         .crop = options->crop,
         .port_range = options->port_range,
         .tunnel_host = options->tunnel_host,

app/src/server.c

@@ -156,6 +156,16 @@ sc_server_sleep(struct sc_server *server, sc_tick deadline) {
     return !stopped;
 }
 
+static const char *
+sc_server_get_codec_name(enum sc_codec codec) {
+    switch (codec) {
+        case SC_CODEC_H264:
+            return "h264";
+        default:
+            return NULL;
+    }
+}
+
 static sc_pid
 execute_server(struct sc_server *server,
                const struct sc_server_params *params) {
@@ -203,6 +213,9 @@ execute_server(struct sc_server *server,
     ADD_PARAM("log_level=%s", log_level_to_server_string(params->log_level));
     ADD_PARAM("bit_rate=%" PRIu32, params->bit_rate);
 
+    if (params->codec != SC_CODEC_H264) {
+        ADD_PARAM("codec=%s", sc_server_get_codec_name(params->codec));
+    }
     if (params->max_size) {
         ADD_PARAM("max_size=%" PRIu16, params->max_size);
     }

app/src/server.h

@@ -25,6 +25,7 @@ struct sc_server_params {
     uint32_t uid;
     const char *req_serial;
     enum sc_log_level log_level;
+    enum sc_codec codec;
     const char *crop;
     const char *codec_options;
     const char *encoder_name;