Open recording file from the recorder thread

The recorder opened the target file from the packet sink open()
callback, called by the demuxer. Only then the recorder thread was
started.

One golden rule for the recorder is to never block the demuxer for I/O,
because it would impact mirroring. This rule is respected on recording
packets, but not for the initial recorder opening.

Therefore, start the recorder thread from sc_recorder_init(), open the
file immediately from the recorder thread, then make it wait for the
stream to start (on packet sink open()).

Now that the recorder can report errors directly (rather than making the
demuxer call fail), it is possible to report file opening error even
before the packet sink is open.

app/src/recorder.c

@@ -132,10 +132,76 @@ sc_recorder_write(struct sc_recorder *recorder, AVPacket *packet) {
     return av_write_frame(recorder->ctx, packet) >= 0;
 }
 
-static int
-run_recorder(void *data) {
-    struct sc_recorder *recorder = data;
+static bool
+sc_recorder_open_output_file(struct sc_recorder *recorder) {
+    const char *format_name = sc_recorder_get_format_name(recorder->format);
+    assert(format_name);
+    const AVOutputFormat *format = find_muxer(format_name);
+    if (!format) {
+        LOGE("Could not find muxer");
+        return false;
+    }
 
+    recorder->ctx = avformat_alloc_context();
+    if (!recorder->ctx) {
+        LOG_OOM();
+        return false;
+    }
+
+    int ret = avio_open(&recorder->ctx->pb, recorder->filename,
+                        AVIO_FLAG_WRITE);
+    if (ret < 0) {
+        LOGE("Failed to open output file: %s", recorder->filename);
+        avformat_free_context(recorder->ctx);
+        return false;
+    }
+
+    // contrary to the deprecated API (av_oformat_next()), av_muxer_iterate()
+    // 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 *) format;
+
+    av_dict_set(&recorder->ctx->metadata, "comment",
+                "Recorded by scrcpy " SCRCPY_VERSION, 0);
+
+    LOGI("Recording started to %s file: %s", format_name, recorder->filename);
+    return true;
+}
+
+static void
+sc_recorder_close_output_file(struct sc_recorder *recorder) {
+    avio_close(recorder->ctx->pb);
+    avformat_free_context(recorder->ctx);
+}
+
+static bool
+sc_recorder_wait_video_stream(struct sc_recorder *recorder) {
+    sc_mutex_lock(&recorder->mutex);
+    while (!recorder->codec && !recorder->stopped) {
+        sc_cond_wait(&recorder->stream_cond, &recorder->mutex);
+    }
+    const AVCodec *codec = recorder->codec;
+    sc_mutex_unlock(&recorder->mutex);
+
+    if (codec) {
+        AVStream *ostream = avformat_new_stream(recorder->ctx, codec);
+        if (!ostream) {
+            return false;
+        }
+
+        ostream->codecpar->codec_type = AVMEDIA_TYPE_VIDEO;
+        ostream->codecpar->codec_id = codec->id;
+        ostream->codecpar->format = AV_PIX_FMT_YUV420P;
+        ostream->codecpar->width = recorder->declared_frame_size.width;
+        ostream->codecpar->height = recorder->declared_frame_size.height;
+    }
+
+    return true;
+}
+
+static bool
+sc_recorder_process_packets(struct sc_recorder *recorder) {
     int64_t pts_origin = AV_NOPTS_VALUE;
 
     // We can write a packet only once we received the next one so that we can
@@ -206,42 +272,70 @@ run_recorder(void *data) {
         if (!ok) {
             LOGE("Could not record packet");
 
-            sc_mutex_lock(&recorder->mutex);
-            recorder->failed = true;
-            // discard pending packets
-            sc_recorder_queue_clear(&recorder->queue);
-            sc_mutex_unlock(&recorder->mutex);
-            break;
+            return false;
         }
 
         previous = rec;
     }
 
-    if (!recorder->failed) {
-        if (recorder->header_written) {
-            int ret = av_write_trailer(recorder->ctx);
-            if (ret < 0) {
-                LOGE("Failed to write trailer to %s", recorder->filename);
-                recorder->failed = true;
-            }
-        } else {
-            // the recorded file is empty
-            recorder->failed = true;
-        }
+    if (!recorder->header_written) {
+        // the recorded file is empty
+        return false;
     }
 
-    if (recorder->failed) {
-        LOGE("Recording failed to %s", recorder->filename);
-    } else {
+    int ret = av_write_trailer(recorder->ctx);
+    if (ret < 0) {
+        LOGE("Failed to write trailer to %s", recorder->filename);
+        return false;
+    }
+
+    return true;
+}
+
+static bool
+sc_recorder_record(struct sc_recorder *recorder) {
+    bool ok = sc_recorder_open_output_file(recorder);
+    if (!ok) {
+        return false;
+    }
+
+    ok = sc_recorder_wait_video_stream(recorder);
+    if (!ok) {
+        sc_recorder_close_output_file(recorder);
+        return false;
+    }
+
+    // If recorder->stopped, process any queued packet anyway
+
+    ok = sc_recorder_process_packets(recorder);
+    sc_recorder_close_output_file(recorder);
+    return ok;
+}
+
+static int
+run_recorder(void *data) {
+    struct sc_recorder *recorder = data;
+
+    bool success = sc_recorder_record(recorder);
+
+    sc_mutex_lock(&recorder->mutex);
+    // Prevent the producer to push any new packet
+    recorder->stopped = true;
+    // Discard pending packets
+    sc_recorder_queue_clear(&recorder->queue);
+    sc_mutex_unlock(&recorder->mutex);
+
+    if (success) {
         const char *format_name = sc_recorder_get_format_name(recorder->format);
         LOGI("Recording complete to %s file: %s", format_name,
                                                   recorder->filename);
+    } else {
+        LOGE("Recording failed to %s", recorder->filename);
     }
 
     LOGD("Recorder thread ended");
 
-    recorder->cbs->on_ended(recorder, !recorder->failed,
-                            recorder->cbs_userdata);
+    recorder->cbs->on_ended(recorder, success, recorder->cbs_userdata);
 
     return 0;
 }
@@ -252,81 +346,28 @@ sc_recorder_packet_sink_open(struct sc_packet_sink *sink,
     struct sc_recorder *recorder = DOWNCAST(sink);
     assert(codec);
 
-    const char *format_name = sc_recorder_get_format_name(recorder->format);
-    assert(format_name);
-    const AVOutputFormat *format = find_muxer(format_name);
-    if (!format) {
-        LOGE("Could not find muxer");
-        return false;
-    }
-
-    recorder->ctx = avformat_alloc_context();
-    if (!recorder->ctx) {
-        LOG_OOM();
+    sc_mutex_lock(&recorder->mutex);
+    if (recorder->stopped) {
+        sc_mutex_unlock(&recorder->mutex);
         return false;
     }
 
-    // contrary to the deprecated API (av_oformat_next()), av_muxer_iterate()
-    // 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 *) format;
-
-    av_dict_set(&recorder->ctx->metadata, "comment",
-                "Recorded by scrcpy " SCRCPY_VERSION, 0);
-
-    AVStream *ostream = avformat_new_stream(recorder->ctx, codec);
-    if (!ostream) {
-        goto error_avformat_free_context;
-    }
-
-    ostream->codecpar->codec_type = AVMEDIA_TYPE_VIDEO;
-    ostream->codecpar->codec_id = codec->id;
-    ostream->codecpar->format = AV_PIX_FMT_YUV420P;
-    ostream->codecpar->width = recorder->declared_frame_size.width;
-    ostream->codecpar->height = recorder->declared_frame_size.height;
-
-    int ret = avio_open(&recorder->ctx->pb, recorder->filename,
-                        AVIO_FLAG_WRITE);
-    if (ret < 0) {
-        LOGE("Failed to open output file: %s", recorder->filename);
-        // ostream will be cleaned up during context cleaning
-        goto error_avformat_free_context;
-    }
-
-    LOGD("Starting recorder thread");
-    bool ok = sc_thread_create(&recorder->thread, run_recorder,
-                               "scrcpy-recorder", recorder);
-    if (!ok) {
-        LOGE("Could not start recorder thread");
-        goto error_avio_close;
-    }
-
-    LOGI("Recording started to %s file: %s", format_name, recorder->filename);
+    recorder->codec = codec;
+    sc_cond_signal(&recorder->stream_cond);
+    sc_mutex_unlock(&recorder->mutex);
 
     return true;
-
-error_avio_close:
-    avio_close(recorder->ctx->pb);
-error_avformat_free_context:
-    avformat_free_context(recorder->ctx);
-
-    return false;
 }
 
 static void
 sc_recorder_packet_sink_close(struct sc_packet_sink *sink) {
     struct sc_recorder *recorder = DOWNCAST(sink);
 
     sc_mutex_lock(&recorder->mutex);
+    // EOS also stops the recorder
     recorder->stopped = true;
     sc_cond_signal(&recorder->queue_cond);
     sc_mutex_unlock(&recorder->mutex);
-
-    sc_thread_join(&recorder->thread, NULL);
-
-    avio_close(recorder->ctx->pb);
-    avformat_free_context(recorder->ctx);
 }
 
 static bool
@@ -335,10 +376,9 @@ sc_recorder_packet_sink_push(struct sc_packet_sink *sink,
     struct sc_recorder *recorder = DOWNCAST(sink);
 
     sc_mutex_lock(&recorder->mutex);
-    assert(!recorder->stopped);
 
-    if (recorder->failed) {
-        // reject any new packet (this will stop the stream)
+    if (recorder->stopped) {
+        // reject any new packet
         sc_mutex_unlock(&recorder->mutex);
         return false;
     }
@@ -378,11 +418,17 @@ sc_recorder_init(struct sc_recorder *recorder, const char *filename,
         goto error_mutex_destroy;
     }
 
+    ok = sc_cond_init(&recorder->stream_cond);
+    if (!ok) {
+        goto error_queue_cond_destroy;
+    }
+
     sc_queue_init(&recorder->queue);
     recorder->stopped = false;
-    recorder->failed = false;
     recorder->header_written = false;
 
+    recorder->codec = NULL;
+
     recorder->format = format;
     recorder->declared_frame_size = declared_frame_size;
 
@@ -398,8 +444,19 @@ sc_recorder_init(struct sc_recorder *recorder, const char *filename,
 
     recorder->packet_sink.ops = &ops;
 
+    ok = sc_thread_create(&recorder->thread, run_recorder, "scrcpy-recorder",
+                          recorder);
+    if (!ok) {
+        LOGE("Could not start recorder thread");
+        goto error_stream_cond_destroy;
+    }
+
     return true;
 
+error_stream_cond_destroy:
+    sc_cond_destroy(&recorder->stream_cond);
+error_queue_cond_destroy:
+    sc_cond_destroy(&recorder->queue_cond);
 error_mutex_destroy:
     sc_mutex_destroy(&recorder->mutex);
 error_free_filename:
@@ -408,8 +465,23 @@ sc_recorder_init(struct sc_recorder *recorder, const char *filename,
     return false;
 }
 
+void
+sc_recorder_stop(struct sc_recorder *recorder) {
+    sc_mutex_lock(&recorder->mutex);
+    recorder->stopped = true;
+    sc_cond_signal(&recorder->queue_cond);
+    sc_cond_signal(&recorder->stream_cond);
+    sc_mutex_unlock(&recorder->mutex);
+}
+
+void
+sc_recorder_join(struct sc_recorder *recorder) {
+    sc_thread_join(&recorder->thread, NULL);
+}
+
 void
 sc_recorder_destroy(struct sc_recorder *recorder) {
+    sc_cond_destroy(&recorder->stream_cond);
     sc_cond_destroy(&recorder->queue_cond);
     sc_mutex_destroy(&recorder->mutex);
     free(recorder->filename);

app/src/recorder.h

@@ -31,10 +31,14 @@ struct sc_recorder {
     sc_thread thread;
     sc_mutex mutex;
     sc_cond queue_cond;
-    bool stopped; // set on recorder_close()
-    bool failed; // set on packet write failure
+    // set on sc_recorder_stop(), packet_sink close or recording failure
+    bool stopped;
     struct sc_recorder_queue queue;
 
+    // wake up the recorder thread once the codec in known
+    sc_cond stream_cond;
+    const AVCodec *codec;
+
     const struct sc_recorder_callbacks *cbs;
     void *cbs_userdata;
 };
@@ -50,6 +54,12 @@ sc_recorder_init(struct sc_recorder *recorder, const char *filename,
                  struct sc_size declared_frame_size,
                  const struct sc_recorder_callbacks *cbs, void *cbs_userdata);
 
+void
+sc_recorder_stop(struct sc_recorder *recorder);
+
+void
+sc_recorder_join(struct sc_recorder *recorder);
+
 void
 sc_recorder_destroy(struct sc_recorder *recorder);
 

app/src/scrcpy.c

@@ -660,6 +660,9 @@ scrcpy(struct scrcpy_options *options) {
     if (file_pusher_initialized) {
         sc_file_pusher_stop(&s->file_pusher);
     }
+    if (recorder_initialized) {
+        sc_recorder_stop(&s->recorder);
+    }
     if (screen_initialized) {
         sc_screen_interrupt(&s->screen);
     }
@@ -706,6 +709,7 @@ scrcpy(struct scrcpy_options *options) {
     }
 
     if (recorder_initialized) {
+        sc_recorder_join(&s->recorder);
         sc_recorder_destroy(&s->recorder);
     }
 

app/src/trait/packet_sink.h

@@ -19,6 +19,7 @@ struct sc_packet_sink {
 };
 
 struct sc_packet_sink_ops {
+    /* The codec instance is static, it is valid until the end of the program */
     bool (*open)(struct sc_packet_sink *sink, const AVCodec *codec);
     void (*close)(struct sc_packet_sink *sink);
     bool (*push)(struct sc_packet_sink *sink, const AVPacket *packet);