Support changing video files underway, just like images.

[nageru] / ffmpeg_capture.cpp

diff --git a/ffmpeg_capture.cpp b/ffmpeg_capture.cpp
index 5474c52fd94f511491206e4f8a92b2545bc87475..464b4cb92d292b8b6bb80f458c92715209f6e902 100644 (file)
--- a/ffmpeg_capture.cpp
+++ b/ffmpeg_capture.cpp
@@ -6,6 +6,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <sys/stat.h>
 #include <unistd.h>
 
 extern "C" {
@@ -44,6 +45,19 @@ steady_clock::time_point compute_frame_start(int64_t frame_pts, int64_t pts_orig
        return origin + duration_cast<steady_clock::duration>(pts / rate);
 }
 
+bool changed_since(const std::string &pathname, const timespec &ts)
+{
+       if (ts.tv_sec < 0) {
+               return false;
+       }
+       struct stat buf;
+       if (stat(pathname.c_str(), &buf) != 0) {
+               fprintf(stderr, "%s: Couldn't check for new version, leaving the old in place.\n", pathname.c_str());
+               return false;
+       }
+       return (buf.st_mtim.tv_sec != ts.tv_sec || buf.st_mtim.tv_nsec != ts.tv_nsec);
+}
+
 }  // namespace
 
 FFmpegCapture::FFmpegCapture(const string &filename, unsigned width, unsigned height)
@@ -142,6 +156,18 @@ void FFmpegCapture::producer_thread_func()
 
 bool FFmpegCapture::play_video(const string &pathname)
 {
+       // Note: Call before open, not after; otherwise, there's a race.
+       // (There is now, too, but it tips the correct way. We could use fstat()
+       // if we had the file descriptor.)
+       timespec last_modified;
+       struct stat buf;
+       if (stat(pathname.c_str(), &buf) != 0) {
+               // Probably some sort of protocol, so can't stat.
+               last_modified.tv_sec = -1;
+       } else {
+               last_modified = buf.st_mtim;
+       }
+
        auto format_ctx = avformat_open_input_unique(pathname.c_str(), nullptr, nullptr);
        if (format_ctx == nullptr) {
                fprintf(stderr, "%s: Error opening file\n", pathname.c_str());
@@ -189,9 +215,7 @@ 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;
+       internal_rewind();
        double rate = 1.0;
 
        unique_ptr<SwsContext, decltype(sws_freeContext)*> sws_ctx(nullptr, sws_freeContext);
@@ -211,8 +235,14 @@ bool FFmpegCapture::play_video(const string &pathname)
                                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());
                                }
-                               pts_origin = last_pts = 0;
-                               start = next_frame_start = steady_clock::now();
+                               // If the file has changed since last time, return to get it reloaded.
+                               // Note that depending on how you move the file into place, you might
+                               // end up corrupting the one you're already playing, so this path
+                               // might not trigger.
+                               if (changed_since(pathname, last_modified)) {
+                                       return true;
+                               }
+                               internal_rewind();
                                break;
 
                        case QueuedCommand::CHANGE_RATE:
@@ -263,8 +293,14 @@ 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();
+                       // If the file has changed since last time, return to get it reloaded.
+                       // Note that depending on how you move the file into place, you might
+                       // end up corrupting the one you're already playing, so this path
+                       // might not trigger.
+                       if (changed_since(pathname, last_modified)) {
+                               return true;
+                       }
+                       internal_rewind();
                        continue;
                }
 
@@ -314,3 +350,9 @@ bool FFmpegCapture::play_video(const string &pathname)
        }
        return true;
 }
+
+void FFmpegCapture::internal_rewind()
+{                              
+       pts_origin = last_pts = 0;
+       start = next_frame_start = steady_clock::now();
+}