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>

README.md

@@ -252,10 +252,19 @@ This affects recording orientation.
 The [window may also be rotated](#rotation) independently.
 
 
-#### Encoder
+#### Codec
 
-Some devices have more than one encoder, and some of them may cause issues or
-crash. It is possible to select a different encoder:
+The video codec can be selected:
+
+```bash
+scrcpy --codec=h264  # default
+```
+
+
+##### Encoder
+
+Some devices have more than one encoder for a specific codec, and some of them
+may cause issues or crash. It is possible to select a different encoder:
 
 ```bash
 scrcpy --encoder=OMX.qcom.video.encoder.avc
@@ -265,7 +274,8 @@ To list the available encoders, you can pass an invalid encoder name; the
 error will give the available encoders:
 
 ```bash
-scrcpy --encoder=_
+scrcpy --encoder=_               # for the default codec
+scrcpy --codec=h264 --encoder=_  # for a specific codec
 ```
 
 ### Capture

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;

server/src/main/java/com/genymobile/scrcpy/Options.java

@@ -5,9 +5,12 @@ import android.graphics.Rect;
 import java.util.List;
 
 public class Options {
+    private static final String VIDEO_CODEC_H264 = "h264";
+
     private Ln.Level logLevel = Ln.Level.DEBUG;
     private int uid = -1; // 31-bit non-negative value, or -1
     private int maxSize;
+    private VideoCodec codec = VideoCodec.H264;
     private int bitRate = 8000000;
     private int maxFps;
     private int lockVideoOrientation = -1;
@@ -29,6 +32,7 @@ public class Options {
     private boolean sendDeviceMeta = true; // send device name and size
     private boolean sendFrameMeta = true; // send PTS so that the client may record properly
     private boolean sendDummyByte = true; // write a byte on start to detect connection issues
+    private boolean sendCodecId = true; // write the codec ID (4 bytes) before the stream
 
     public Ln.Level getLogLevel() {
         return logLevel;
@@ -54,6 +58,14 @@ public class Options {
         this.maxSize = maxSize;
     }
 
+    public VideoCodec getCodec() {
+        return codec;
+    }
+
+    public void setCodec(VideoCodec codec) {
+        this.codec = codec;
+    }
+
     public int getBitRate() {
         return bitRate;
     }
@@ -205,4 +217,12 @@ public class Options {
     public void setSendDummyByte(boolean sendDummyByte) {
         this.sendDummyByte = sendDummyByte;
     }
+
+    public boolean getSendCodecId() {
+        return sendCodecId;
+    }
+
+    public void setSendCodecId(boolean sendCodecId) {
+        this.sendCodecId = sendCodecId;
+    }
 }

server/src/main/java/com/genymobile/scrcpy/ScreenEncoder.java

@@ -35,6 +35,7 @@ public class ScreenEncoder implements Device.RotationListener {
 
     private final AtomicBoolean rotationChanged = new AtomicBoolean();
 
+    private final String videoMimeType;
     private final String encoderName;
     private final List<CodecOption> codecOptions;
     private final int bitRate;
@@ -44,7 +45,8 @@ public class ScreenEncoder implements Device.RotationListener {
     private boolean firstFrameSent;
     private int consecutiveErrors;
 
-    public ScreenEncoder(int bitRate, int maxFps, List<CodecOption> codecOptions, String encoderName, boolean downsizeOnError) {
+    public ScreenEncoder(String videoMimeType, int bitRate, int maxFps, List<CodecOption> codecOptions, String encoderName, boolean downsizeOnError) {
+        this.videoMimeType = videoMimeType;
         this.bitRate = bitRate;
         this.maxFps = maxFps;
         this.codecOptions = codecOptions;
@@ -62,8 +64,8 @@ public class ScreenEncoder implements Device.RotationListener {
     }
 
     public void streamScreen(Device device, Callbacks callbacks) throws IOException {
-        MediaCodec codec = createCodec(encoderName);
-        MediaFormat format = createFormat(bitRate, maxFps, codecOptions);
+        MediaCodec codec = createCodec(videoMimeType, encoderName);
+        MediaFormat format = createFormat(videoMimeType, bitRate, maxFps, codecOptions);
         IBinder display = createDisplay();
         device.setRotationListener(this);
         boolean alive;
@@ -194,28 +196,28 @@ public class ScreenEncoder implements Device.RotationListener {
         return !eof;
     }
 
-    private static MediaCodecInfo[] listEncoders() {
+    private static MediaCodecInfo[] listEncoders(String videoMimeType) {
         List<MediaCodecInfo> result = new ArrayList<>();
         MediaCodecList list = new MediaCodecList(MediaCodecList.REGULAR_CODECS);
         for (MediaCodecInfo codecInfo : list.getCodecInfos()) {
-            if (codecInfo.isEncoder() && Arrays.asList(codecInfo.getSupportedTypes()).contains(MediaFormat.MIMETYPE_VIDEO_AVC)) {
+            if (codecInfo.isEncoder() && Arrays.asList(codecInfo.getSupportedTypes()).contains(videoMimeType)) {
                 result.add(codecInfo);
             }
         }
         return result.toArray(new MediaCodecInfo[result.size()]);
     }
 
-    private static MediaCodec createCodec(String encoderName) throws IOException {
+    private static MediaCodec createCodec(String videoMimeType, String encoderName) throws IOException {
         if (encoderName != null) {
             Ln.d("Creating encoder by name: '" + encoderName + "'");
             try {
                 return MediaCodec.createByCodecName(encoderName);
             } catch (IllegalArgumentException e) {
-                MediaCodecInfo[] encoders = listEncoders();
+                MediaCodecInfo[] encoders = listEncoders(videoMimeType);
                 throw new InvalidEncoderException(encoderName, encoders);
             }
         }
-        MediaCodec codec = MediaCodec.createEncoderByType(MediaFormat.MIMETYPE_VIDEO_AVC);
+        MediaCodec codec = MediaCodec.createEncoderByType(videoMimeType);
         Ln.d("Using encoder: '" + codec.getName() + "'");
         return codec;
     }
@@ -237,9 +239,9 @@ public class ScreenEncoder implements Device.RotationListener {
         Ln.d("Codec option set: " + key + " (" + value.getClass().getSimpleName() + ") = " + value);
     }
 
-    private static MediaFormat createFormat(int bitRate, int maxFps, List<CodecOption> codecOptions) {
+    private static MediaFormat createFormat(String videoMimeType, int bitRate, int maxFps, List<CodecOption> codecOptions) {
         MediaFormat format = new MediaFormat();
-        format.setString(MediaFormat.KEY_MIME, MediaFormat.MIMETYPE_VIDEO_AVC);
+        format.setString(MediaFormat.KEY_MIME, videoMimeType);
         format.setInteger(MediaFormat.KEY_BIT_RATE, bitRate);
         // must be present to configure the encoder, but does not impact the actual frame rate, which is variable
         format.setInteger(MediaFormat.KEY_FRAME_RATE, 60);

server/src/main/java/com/genymobile/scrcpy/Server.java

@@ -85,12 +85,13 @@ public final class Server {
         }
 
         try (DesktopConnection connection = DesktopConnection.open(uid, tunnelForward, control, sendDummyByte)) {
+            VideoCodec codec = options.getCodec();
             if (options.getSendDeviceMeta()) {
                 Size videoSize = device.getScreenInfo().getVideoSize();
                 connection.sendDeviceMeta(Device.getDeviceName(), videoSize.getWidth(), videoSize.getHeight());
             }
-            ScreenEncoder screenEncoder = new ScreenEncoder(options.getBitRate(), options.getMaxFps(), codecOptions, options.getEncoderName(),
-                    options.getDownsizeOnError());
+            ScreenEncoder screenEncoder = new ScreenEncoder(codec.getMimeType(), options.getBitRate(), options.getMaxFps(), codecOptions,
+                    options.getEncoderName(), options.getDownsizeOnError());
 
             Controller controller = null;
             if (control) {
@@ -104,6 +105,9 @@ public final class Server {
             try {
                 // synchronous
                 VideoStreamer videoStreamer = new VideoStreamer(connection.getVideoFd(), options.getSendFrameMeta());
+                if (options.getSendCodecId()) {
+                    videoStreamer.writeHeader(codec.getId());
+                }
                 screenEncoder.streamScreen(device, videoStreamer);
             } catch (IOException e) {
                 // this is expected on close
@@ -156,6 +160,13 @@ public final class Server {
                     Ln.Level level = Ln.Level.valueOf(value.toUpperCase(Locale.ENGLISH));
                     options.setLogLevel(level);
                     break;
+                case "codec":
+                    VideoCodec codec = VideoCodec.findByName(value);
+                    if (codec == null) {
+                        throw new IllegalArgumentException("Video codec " + value + " not supported");
+                    }
+                    options.setCodec(codec);
+                    break;
                 case "max_size":
                     int maxSize = Integer.parseInt(value) & ~7; // multiple of 8
                     options.setMaxSize(maxSize);
@@ -237,12 +248,17 @@ public final class Server {
                     boolean sendDummyByte = Boolean.parseBoolean(value);
                     options.setSendDummyByte(sendDummyByte);
                     break;
+                case "send_codec_id":
+                    boolean sendCodecId = Boolean.parseBoolean(value);
+                    options.setSendCodecId(sendCodecId);
+                    break;
                 case "raw_video_stream":
                     boolean rawVideoStream = Boolean.parseBoolean(value);
                     if (rawVideoStream) {
                         options.setSendDeviceMeta(false);
                         options.setSendFrameMeta(false);
                         options.setSendDummyByte(false);
+                        options.setSendCodecId(false);
                     }
                     break;
                 default:

server/src/main/java/com/genymobile/scrcpy/VideoCodec.java

@@ -0,0 +1,34 @@
+package com.genymobile.scrcpy;
+
+import android.media.MediaFormat;
+
+public enum VideoCodec {
+    H264(0x68_32_36_34, "h264", MediaFormat.MIMETYPE_VIDEO_AVC);
+
+    private final int id; // 4-byte ASCII representation of the name
+    private final String name;
+    private final String mimeType;
+
+    VideoCodec(int id, String name, String mimeType) {
+        this.id = id;
+        this.name = name;
+        this.mimeType = mimeType;
+    }
+
+    public int getId() {
+        return id;
+    }
+
+    public String getMimeType() {
+        return mimeType;
+    }
+
+    public static VideoCodec findByName(String name) {
+        for (VideoCodec codec : values()) {
+            if (codec.name.equals(name)) {
+                return codec;
+            }
+        }
+        return null;
+    }
+}

server/src/main/java/com/genymobile/scrcpy/VideoStreamer.java

@@ -21,6 +21,13 @@ public final class VideoStreamer implements ScreenEncoder.Callbacks {
         this.sendFrameMeta = sendFrameMeta;
     }
 
+    public void writeHeader(int codecId) throws IOException {
+        ByteBuffer buffer = ByteBuffer.allocate(4);
+        buffer.putInt(codecId);
+        buffer.flip();
+        IO.writeFully(fd, buffer);
+    }
+
     @Override
     public void onPacket(ByteBuffer codecBuffer, MediaCodec.BufferInfo bufferInfo) throws IOException {
         if (sendFrameMeta) {