Add support for FLAC audio codec

PR #4410 <##4410>

Co-authored-by: Romain Vimont <[email protected]>
Signed-off-by: Romain Vimont <[email protected]>

Author: megapro17

app/data/bash-completion/scrcpy

@@ -97,7 +97,7 @@ _scrcpy() {
             return
             ;;
         --audio-codec)
-            COMPREPLY=($(compgen -W 'opus aac raw' -- "$cur"))
+            COMPREPLY=($(compgen -W 'opus aac flac raw' -- "$cur"))
             return
             ;;
         --video-source)
@@ -125,7 +125,7 @@ _scrcpy() {
             return
             ;;
         --record-format)
-            COMPREPLY=($(compgen -W 'mp4 mkv m4a mka opus aac' -- "$cur"))
+            COMPREPLY=($(compgen -W 'mp4 mkv m4a mka opus aac flac' -- "$cur"))
             return
             ;;
         --render-driver)

app/data/zsh-completion/_scrcpy

@@ -11,7 +11,7 @@ arguments=(
     '--always-on-top[Make scrcpy window always on top \(above other windows\)]'
     '--audio-bit-rate=[Encode the audio at the given bit-rate]'
     '--audio-buffer=[Configure the audio buffering delay (in milliseconds)]'
-    '--audio-codec=[Select the audio codec]:codec:(opus aac raw)'
+    '--audio-codec=[Select the audio codec]:codec:(opus aac flac raw)'
     '--audio-codec-options=[Set a list of comma-separated key\:type=value options for the device audio encoder]'
     '--audio-encoder=[Use a specific MediaCodec audio encoder]'
     '--audio-source=[Select the audio source]:source:(output mic)'
@@ -65,7 +65,7 @@ arguments=(
     '--push-target=[Set the target directory for pushing files to the device by drag and drop]'
     {-r,--record=}'[Record screen to file]:record file:_files'
     '--raw-key-events[Inject key events for all input keys, and ignore text events]'
-    '--record-format=[Force recording format]:format:(mp4 mkv m4a mka opus aac)'
+    '--record-format=[Force recording format]:format:(mp4 mkv m4a mka opus aac flac)'
     '--render-driver=[Request SDL to use the given render driver]:driver name:(direct3d opengl opengles2 opengles metal software)'
     '--require-audio=[Make scrcpy fail if audio is enabled but does not work]'
     '--rotation=[Set the initial display rotation]:rotation values:(0 1 2 3)'

app/scrcpy.1

@@ -35,7 +35,7 @@ Default is 50.
 
 .TP
 .BI "\-\-audio\-codec " name
-Select an audio codec (opus, aac or raw).
+Select an audio codec (opus, aac, flac or raw).
 
 Default is opus.
 
@@ -355,7 +355,7 @@ Inject key events for all input keys, and ignore text events.
 
 .TP
 .BI "\-\-record\-format " format
-Force recording format (mp4, mkv, m4a, mka, opus or aac).
+Force recording format (mp4, mkv, m4a, mka, opus, aac or flac).
 
 .TP
 .BI "\-\-render\-driver " name

app/src/cli.c

@@ -152,7 +152,7 @@ static const struct sc_option options[] = {
         .longopt_id = OPT_AUDIO_CODEC,
         .longopt = "audio-codec",
         .argdesc = "name",
-        .text = "Select an audio codec (opus, aac or raw).\n"
+        .text = "Select an audio codec (opus, aac, flac or raw).\n"
                 "Default is opus.",
     },
     {
@@ -594,7 +594,8 @@ static const struct sc_option options[] = {
         .longopt_id = OPT_RECORD_FORMAT,
         .longopt = "record-format",
         .argdesc = "format",
-        .text = "Force recording format (mp4, mkv, m4a, mka, opus or aac).",
+        .text = "Force recording format (mp4, mkv, m4a, mka, opus, aac or "
+                "flac).",
     },
     {
         .longopt_id = OPT_RENDER_DRIVER,
@@ -1626,6 +1627,9 @@ get_record_format(const char *name) {
     if (!strcmp(name, "aac")) {
         return SC_RECORD_FORMAT_AAC;
     }
+    if (!strcmp(name, "flac")) {
+        return SC_RECORD_FORMAT_FLAC;
+    }
     return 0;
 }
 
@@ -1695,11 +1699,15 @@ parse_audio_codec(const char *optarg, enum sc_codec *codec) {
         *codec = SC_CODEC_AAC;
         return true;
     }
+    if (!strcmp(optarg, "flac")) {
+        *codec = SC_CODEC_FLAC;
+        return true;
+    }
     if (!strcmp(optarg, "raw")) {
         *codec = SC_CODEC_RAW;
         return true;
     }
-    LOGE("Unsupported audio codec: %s (expected opus, aac or raw)", optarg);
+    LOGE("Unsupported audio codec: %s (expected opus, aac, flac or raw)", optarg);
     return false;
 }
 
@@ -2376,6 +2384,16 @@ parse_args_with_getopt(struct scrcpy_cli_args *args, int argc, char *argv[],
                  "(try with --audio-codec=aac)");
             return false;
         }
+        if (opts->record_format == SC_RECORD_FORMAT_FLAC
+                && opts->audio_codec != SC_CODEC_FLAC) {
+            LOGE("Recording to FLAC file requires a FLAC audio stream "
+                 "(try with --audio-codec=flac)");
+            return false;
+        }
+    }
+
+    if (opts->audio_codec == SC_CODEC_FLAC && opts->audio_bit_rate) {
+        LOGW("--audio-bit-rate is ignored for FLAC audio codec");
     }
 
     if (opts->audio_codec == SC_CODEC_RAW) {

app/src/demuxer.c

@@ -25,7 +25,8 @@ sc_demuxer_to_avcodec_id(uint32_t codec_id) {
 #define SC_CODEC_ID_H265 UINT32_C(0x68323635) // "h265" in ASCII
 #define SC_CODEC_ID_AV1 UINT32_C(0x00617631) // "av1" in ASCII
 #define SC_CODEC_ID_OPUS UINT32_C(0x6f707573) // "opus" in ASCII
-#define SC_CODEC_ID_AAC UINT32_C(0x00616163) // "aac in ASCII"
+#define SC_CODEC_ID_AAC UINT32_C(0x00616163) // "aac" in ASCII
+#define SC_CODEC_ID_FLAC UINT32_C(0x666c6163) // "flac" in ASCII
 #define SC_CODEC_ID_RAW UINT32_C(0x00726177) // "raw" in ASCII
     switch (codec_id) {
         case SC_CODEC_ID_H264:
@@ -43,6 +44,8 @@ sc_demuxer_to_avcodec_id(uint32_t codec_id) {
             return AV_CODEC_ID_OPUS;
         case SC_CODEC_ID_AAC:
             return AV_CODEC_ID_AAC;
+        case SC_CODEC_ID_FLAC:
+            return AV_CODEC_ID_FLAC;
         case SC_CODEC_ID_RAW:
             return AV_CODEC_ID_PCM_S16LE;
         default:
@@ -207,6 +210,11 @@ run_demuxer(void *data) {
         codec_ctx->channels = 2;
 #endif
         codec_ctx->sample_rate = 48000;
+
+        if (raw_codec_id == SC_CODEC_ID_FLAC) {
+            // The sample_fmt is not set by the FLAC decoder
+            codec_ctx->sample_fmt = AV_SAMPLE_FMT_S16;
+        }
     }
 
     if (avcodec_open2(codec_ctx, codec, NULL) < 0) {

app/src/options.h

@@ -25,14 +25,16 @@ enum sc_record_format {
     SC_RECORD_FORMAT_MKA,
     SC_RECORD_FORMAT_OPUS,
     SC_RECORD_FORMAT_AAC,
+    SC_RECORD_FORMAT_FLAC,
 };
 
 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
         || fmt == SC_RECORD_FORMAT_OPUS
-        || fmt == SC_RECORD_FORMAT_AAC;
+        || fmt == SC_RECORD_FORMAT_AAC
+        || fmt == SC_RECORD_FORMAT_FLAC;
 }
 
 enum sc_codec {
@@ -41,6 +43,7 @@ enum sc_codec {
     SC_CODEC_AV1,
     SC_CODEC_OPUS,
     SC_CODEC_AAC,
+    SC_CODEC_FLAC,
     SC_CODEC_RAW,
 };
 

app/src/recorder.c

@@ -69,6 +69,8 @@ sc_recorder_get_format_name(enum sc_record_format format) {
             return "matroska";
         case SC_RECORD_FORMAT_OPUS:
             return "opus";
+        case SC_RECORD_FORMAT_FLAC:
+            return "flac";
         default:
             return NULL;
     }

app/src/server.c

@@ -178,6 +178,8 @@ sc_server_get_codec_name(enum sc_codec codec) {
             return "opus";
         case SC_CODEC_AAC:
             return "aac";
+        case SC_CODEC_FLAC:
+            return "flac";
         case SC_CODEC_RAW:
             return "raw";
         default:

doc/audio.md

@@ -62,12 +62,13 @@ scrcpy --audio-source=mic --no-video --no-playback --record=file.opus
 
 ## Codec
 
-The audio codec can be selected. The possible values are `opus` (default), `aac`
-and `raw` (uncompressed PCM 16-bit LE):
+The audio codec can be selected. The possible values are `opus` (default),
+`aac`, `flac` and `raw` (uncompressed PCM 16-bit LE):
 
 ```bash
 scrcpy --audio-codec=opus  # default
 scrcpy --audio-codec=aac
+scrcpy --audio-codec=flac
 scrcpy --audio-codec=raw
 ```
 
@@ -80,7 +81,14 @@ then your device has no Opus encoder: try `scrcpy --audio-codec=aac`.
 For advanced usage, to pass arbitrary parameters to the [`MediaFormat`],
 check `--audio-codec-options` in the manpage or in `scrcpy --help`.
 
+For example, to change the [FLAC compression level]:
+
+```bash
+scrcpy --audio-codec=flac --audio-codec-options=flac-compression-level=8
+```
+
 [`MediaFormat`]: https://developer.android.com/reference/android/media/MediaFormat
+[FLAC compression level]: https://developer.android.com/reference/android/media/MediaFormat#KEY_FLAC_COMPRESSION_LEVEL
 
 
 ## Encoder

doc/recording.md

@@ -18,7 +18,8 @@ To record only the audio:
 ```bash
 scrcpy --no-video --record=file.opus
 scrcpy --no-video --audio-codec=aac --record=file.aac
-# .m4a/.mp4 and .mka/.mkv are also supported for both opus and aac
+scrcpy --no-video --audio-codec=flac --record=file.flac
+# .m4a/.mp4 and .mka/.mkv are also supported for opus, aac and flac
 ```
 
 Timestamps are captured on the device, so [packet delay variation] does not
@@ -35,6 +36,7 @@ client side. Several formats (containers) are supported:
  - MP4 (`.mp4`, `.m4a`, `.aac`)
  - Matroska (`.mkv`, `.mka`)
  - OPUS (`.opus`)
+ - FLAC (`.flac`)
 
 The container is automatically selected based on the filename.
 

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

@@ -5,6 +5,7 @@
 public enum AudioCodec implements Codec {
     OPUS(0x6f_70_75_73, "opus", MediaFormat.MIMETYPE_AUDIO_OPUS),
     AAC(0x00_61_61_63, "aac", MediaFormat.MIMETYPE_AUDIO_AAC),
+    FLAC(0x66_6c_61_63, "flac", MediaFormat.MIMETYPE_AUDIO_FLAC),
     RAW(0x00_72_61_77, "raw", MediaFormat.MIMETYPE_AUDIO_RAW);
 
     private final int id; // 4-byte ASCII representation of the name

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

@@ -5,6 +5,7 @@
 import java.io.FileDescriptor;
 import java.io.IOException;
 import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
 import java.util.Arrays;
 
 public final class Streamer {
@@ -29,6 +30,7 @@ public Streamer(FileDescriptor fd, Codec codec, boolean sendCodecMeta, boolean s
     public Codec getCodec() {
         return codec;
     }
+
     public void writeAudioHeader() throws IOException {
         if (sendCodecMeta) {
             ByteBuffer buffer = ByteBuffer.allocate(4);
@@ -61,8 +63,12 @@ public void writeDisableStream(boolean error) throws IOException {
     }
 
     public void writePacket(ByteBuffer buffer, long pts, boolean config, boolean keyFrame) throws IOException {
-        if (config && codec == AudioCodec.OPUS) {
-            fixOpusConfigPacket(buffer);
+        if (config) {
+            if (codec == AudioCodec.OPUS) {
+                fixOpusConfigPacket(buffer);
+            } else if (codec == AudioCodec.FLAC) {
+                fixFlacConfigPacket(buffer);
+            }
         }
 
         if (sendFrameMeta) {
@@ -140,4 +146,41 @@ private static void fixOpusConfigPacket(ByteBuffer buffer) throws IOException {
         // Set the buffer to point to the OPUS header slice
         buffer.limit(buffer.position() + size);
     }
+
+    private static void fixFlacConfigPacket(ByteBuffer buffer) throws IOException {
+        // 00000000  66 4c 61 43 00 00 00 22                           |fLaC..."        |
+        // -------------- BELOW IS THE PART WE MUST PUT AS EXTRADATA  -------------------
+        // 00000000                           10 00 10 00 00 00 00 00  |        ........|
+        // 00000010  00 00 0b b8 02 f0 00 00  00 00 00 00 00 00 00 00  |................|
+        // 00000020  00 00 00 00 00 00 00 00  00 00                    |..........      |
+        // ------------------------------------------------------------------------------
+        // 00000020                                 84 00 00 28 20 00  |          ...( .|
+        // 00000030  00 00 72 65 66 65 72 65  6e 63 65 20 6c 69 62 46  |..reference libF|
+        // 00000040  4c 41 43 20 31 2e 33 2e  32 20 32 30 32 32 31 30  |LAC 1.3.2 202210|
+        // 00000050  32 32 00 00 00 00                                 |22....|
+        //
+        // <https://developer.android.com/reference/android/media/MediaCodec#CSD>
+
+        if (buffer.remaining() < 8) {
+            throw new IOException("Not enough data in FLAC config packet");
+        }
+
+        final byte[] flacHeaderId = {'f', 'L', 'a', 'C'};
+        byte[] idBuffer = new byte[4];
+        buffer.get(idBuffer);
+        if (!Arrays.equals(idBuffer, flacHeaderId)) {
+            throw new IOException("FLAC header not found");
+        }
+
+        // The size is in big-endian
+        buffer.order(ByteOrder.BIG_ENDIAN);
+
+        int size = buffer.getInt();
+        if (buffer.remaining() < size) {
+            throw new IOException("Not enough data in FLAC header (invalid size: " + size + ")");
+        }
+
+        // Set the buffer to point to the FLAC header slice
+        buffer.limit(buffer.position() + size);
+    }
 }