Add support for changing the playback rate.

[nageru] / ffmpeg_capture.cpp

diff --git a/ffmpeg_capture.cpp b/ffmpeg_capture.cpp
index bb41a35a4dc01b9909cb374967c65a0153216179..77af9e654067f643ca411c7641ae11963a115414 100644 (file)
--- a/ffmpeg_capture.cpp
+++ b/ffmpeg_capture.cpp
@@ -36,6 +36,16 @@ using namespace std;
 using namespace std::chrono;
 using namespace bmusb;
 
+namespace {
+
+steady_clock::time_point compute_frame_start(int64_t frame_pts, int64_t pts_origin, const AVRational &video_timebase, const steady_clock::time_point &origin, double rate)
+{
+       const duration<double> pts((frame_pts - pts_origin) * double(video_timebase.num) / double(video_timebase.den));
+       return origin + duration_cast<steady_clock::duration>(pts / rate);
+}
+
+}  // namespace
+
 FFmpegCapture::FFmpegCapture(const string &filename, unsigned width, unsigned height)
        : filename(filename), width(width), height(height)
 {
@@ -179,7 +189,10 @@ bool FFmpegCapture::play_video(const string &pathname)
        unique_ptr<AVCodecContext, decltype(avcodec_close)*> codec_ctx_cleanup(
                codec_ctx.get(), avcodec_close);
 
+       int64_t pts_origin = 0, last_pts = 0;
        steady_clock::time_point start = steady_clock::now();
+       steady_clock::time_point next_frame_start = start;
+       double rate = 1.0;
 
        unique_ptr<SwsContext, decltype(sws_freeContext)*> sws_ctx(nullptr, sws_freeContext);
        int sws_last_width = -1, sws_last_height = -1;
@@ -193,12 +206,20 @@ bool FFmpegCapture::play_video(const string &pathname)
                        swap(commands, command_queue);
                }
                for (const QueuedCommand &cmd : commands) {
-                       if (cmd.command == QueuedCommand::REWIND) {
+                       switch (cmd.command) {
+                       case QueuedCommand::REWIND:
                                if (av_seek_frame(format_ctx.get(), /*stream_index=*/-1, /*timestamp=*/0, /*flags=*/0) < 0) {
                                        fprintf(stderr, "%s: Rewind failed, stopping play.\n", pathname.c_str());
                                }
-                               start = steady_clock::now();
-                               continue;
+                               pts_origin = last_pts = 0;
+                               start = next_frame_start = steady_clock::now();
+                               break;
+
+                       case QueuedCommand::CHANGE_RATE:
+                               start = next_frame_start;
+                               pts_origin = last_pts;
+                               rate = cmd.new_rate;
+                               break;
                        }
                }
 
@@ -242,6 +263,7 @@ bool FFmpegCapture::play_video(const string &pathname)
                                fprintf(stderr, "%s: Rewind failed, not looping.\n", pathname.c_str());
                                return true;
                        }
+                       pts_origin = last_pts = 0;
                        start = steady_clock::now();
                        continue;
                }
@@ -268,8 +290,8 @@ bool FFmpegCapture::play_video(const string &pathname)
                video_format.has_signal = true;
                video_format.is_connected = true;
 
-               const duration<double> pts(frame->pts * double(video_timebase.num) / double(video_timebase.den));
-               const steady_clock::time_point frame_start = start + duration_cast<steady_clock::duration>(pts);
+               next_frame_start = compute_frame_start(frame->pts, pts_origin, video_timebase, start, rate);
+               last_pts = frame->pts;
 
                FrameAllocator::Frame video_frame = video_frame_allocator->alloc_frame();
                if (video_frame.data != nullptr) {
@@ -277,7 +299,7 @@ bool FFmpegCapture::play_video(const string &pathname)
                        int linesizes[4] = { int(video_format.stride), 0, 0, 0 };
                        sws_scale(sws_ctx.get(), frame->data, frame->linesize, 0, frame->height, pic_data, linesizes);
                        video_frame.len = video_format.stride * height;
-                       video_frame.received_timestamp = frame_start;
+                       video_frame.received_timestamp = next_frame_start;
                }
 
                FrameAllocator::Frame audio_frame;
@@ -285,7 +307,8 @@ bool FFmpegCapture::play_video(const string &pathname)
                 audio_format.bits_per_sample = 32;
                 audio_format.num_channels = 8;
 
-               this_thread::sleep_until(frame_start);
+               // TODO: Make it interruptable somehow.
+               this_thread::sleep_until(next_frame_start);
                frame_callback(timecode++,
                        video_frame, 0, video_format,
                        audio_frame, 0, audio_format);