Add compat support for FFmpeg < 5.1

The new chlayout API has been introduced in FFmpeg 5.1. Use the old
channel_layout API on older versions.

PR #3757 <Genymobile/scrcpy#3757>

Author: rom1v

app/src/audio_player.c

@@ -93,11 +93,19 @@ static bool
 sc_audio_player_frame_sink_open(struct sc_frame_sink *sink,
                                 const AVCodecContext *ctx) {
     struct sc_audio_player *ap = DOWNCAST(sink);
+#ifdef SCRCPY_LAVU_HAS_CHLAYOUT
+    assert(ctx->ch_layout.nb_channels > 0);
+    unsigned nb_channels = ctx->ch_layout.nb_channels;
+#else
+    int tmp = av_get_channel_layout_nb_channels(ctx->channel_layout);
+    assert(tmp > 0);
+    unsigned nb_channels = tmp;
+#endif
 
     SDL_AudioSpec desired = {
         .freq = ctx->sample_rate,
         .format = SC_SDL_SAMPLE_FMT,
-        .channels = ctx->ch_layout.nb_channels,
+        .channels = nb_channels,
         .samples = SC_AUDIO_OUTPUT_BUFFER_SAMPLES,
         .callback = sc_audio_player_sdl_callback,
         .userdata = ap,
@@ -118,13 +126,20 @@ sc_audio_player_frame_sink_open(struct sc_frame_sink *sink,
     ap->swr_ctx = swr_ctx;
 
     assert(ctx->sample_rate > 0);
-    assert(ctx->ch_layout.nb_channels > 0);
     assert(!av_sample_fmt_is_planar(SC_AV_SAMPLE_FMT));
+
     int out_bytes_per_sample = av_get_bytes_per_sample(SC_AV_SAMPLE_FMT);
     assert(out_bytes_per_sample > 0);
 
+#ifdef SCRCPY_LAVU_HAS_CHLAYOUT
     av_opt_set_chlayout(swr_ctx, "in_chlayout", &ctx->ch_layout, 0);
     av_opt_set_chlayout(swr_ctx, "out_chlayout", &ctx->ch_layout, 0);
+#else
+    av_opt_set_channel_layout(swr_ctx, "in_channel_layout",
+                              ctx->channel_layout, 0);
+    av_opt_set_channel_layout(swr_ctx, "out_channel_layout",
+                              ctx->channel_layout, 0);
+#endif
 
     av_opt_set_int(swr_ctx, "in_sample_rate", ctx->sample_rate, 0);
     av_opt_set_int(swr_ctx, "out_sample_rate", ctx->sample_rate, 0);
@@ -139,7 +154,7 @@ sc_audio_player_frame_sink_open(struct sc_frame_sink *sink,
     }
 
     ap->sample_rate = ctx->sample_rate;
-    ap->nb_channels = ctx->ch_layout.nb_channels;
+    ap->nb_channels = nb_channels;
     ap->out_bytes_per_sample = out_bytes_per_sample;
 
     size_t bytebuf_size = samples_to_bytes(ap, SC_BYTEBUF_SIZE_IN_SAMPLES);

app/src/compat.h

@@ -37,6 +37,13 @@
 # define SCRCPY_LAVF_HAS_AVFORMATCONTEXT_URL
 #endif
 
+// Not documented in ffmpeg/doc/APIchanges, but the channel_layout API
+// has been replaced by chlayout in FFmpeg commit
+// f423497b455da06c1337846902c770028760e094.
+#if LIBAVUTIL_VERSION_INT >= AV_VERSION_INT(57, 23, 100)
+# define SCRCPY_LAVU_HAS_CHLAYOUT
+#endif
+
 #if SDL_VERSION_ATLEAST(2, 0, 6)
 // <https://github.com/libsdl-org/SDL/commit/d7a318de563125e5bb465b1000d6bc9576fbc6fc>
 # define SCRCPY_SDL_HAS_HINT_TOUCH_MOUSE_EVENTS

app/src/decoder.c

@@ -53,8 +53,13 @@ sc_decoder_open(struct sc_decoder *decoder, const AVCodec *codec) {
         decoder->codec_ctx->pix_fmt = AV_PIX_FMT_YUV420P;
     } else {
         // Hardcoded audio properties
+#ifdef SCRCPY_LAVU_HAS_CHLAYOUT
         decoder->codec_ctx->ch_layout =
             (AVChannelLayout) AV_CHANNEL_LAYOUT_STEREO;
+#else
+        decoder->codec_ctx->channel_layout = AV_CH_LAYOUT_STEREO;
+        decoder->codec_ctx->channels = 2;
+#endif
         decoder->codec_ctx->sample_rate = 48000;
     }
 

app/src/recorder.c

@@ -216,7 +216,12 @@ sc_recorder_wait_audio_stream(struct sc_recorder *recorder) {
 
         stream->codecpar->codec_type = AVMEDIA_TYPE_AUDIO;
         stream->codecpar->codec_id = codec->id;
+#ifdef SCRCPY_LAVU_HAS_CHLAYOUT
         stream->codecpar->ch_layout.nb_channels = 2;
+#else
+        stream->codecpar->channel_layout = AV_CH_LAYOUT_STEREO;
+        stream->codecpar->channels = 2;
+#endif
         stream->codecpar->sample_rate = 48000;
 
         recorder->audio_stream_index = stream->index;