avdevice/decklink: remove pthread dependency

Purpose: avdevice/decklink: Removed pthread dependency by replacing
semaphore used in code appropriately.  Doing so makes it easier to
build ffmpeg using Visual C++ on Windows.  This is a contination of
Kyle Schwarz's "avdevice/decklink: Remove pthread dependency" patch
that is available at https://patchwork.ffmpeg.org/patch/2654/ .  This
patch wasn't accepted, and as far as I can tell, there was no
follow-up after it was rejected.

Notes: Used Visual Studio 2015 (with update 3) for this.

Comments:

-- configure: Eliminated pthreads dependency for decklink_indev_deps
   and decklink_outdev_deps and replaced with threads dependency

-- libavdevice/decklink_common.cpp / .h:
a) Eliminated semaphore and replaced with a combination of a mutex,
   condition variable, and a counter (frames_buffer_available_spots).
b) Removed include of pthread.h and semaphore.h and now using
   libavutil/thread.h instead.

-- libavdevice/decklink_dec.cpp: Eliminated include of pthread.h and
   semaphore.h.

-- libavdevice/decklink_enc.cpp:
a) Eliminated include of pthread.h and semaphore.h.
b) Replaced use of semaphore with the equivalent using a combination
   of a mutex, condition variable, and a counter
   (frames_buffer_available_spots).  In theory, libavutil/thread.h and
   the associated code could have been modified instead to add
   cross-platform implementations of the sem_ functions, but an
   inspection of the ffmpeg source base indicates that there are only
   two cases in which semaphores are used (including this one that was
   replaced), so it was deemed to not be worth the effort.

Signed-off-by: Marton Balint <cus@passwd.hu>

diff --git a/configure b/configure
index 98f7828489e904a43ef5c85d307a94051db83460..3f2811a5b369b67003771afca4cdb44faaed009d 100755 (executable)
--- a/configure
+++ b/configure
@@ -2995,9 +2995,9 @@ avfoundation_indev_deps="pthreads"
 avfoundation_indev_extralibs="-framework Foundation -framework AVFoundation -framework CoreVideo -framework CoreMedia"
 bktr_indev_deps_any="dev_bktr_ioctl_bt848_h machine_ioctl_bt848_h dev_video_bktr_ioctl_bt848_h dev_ic_bt8xx_h"
 caca_outdev_deps="libcaca"
-decklink_indev_deps="decklink pthreads"
+decklink_indev_deps="decklink threads"
 decklink_indev_extralibs="-lstdc++"
-decklink_outdev_deps="decklink pthreads"
+decklink_outdev_deps="decklink threads"
 decklink_outdev_extralibs="-lstdc++"
 dshow_indev_deps="IBaseFilter"
 dshow_indev_extralibs="-lpsapi -lole32 -lstrmiids -luuid -loleaut32 -lshlwapi"

diff --git a/libavdevice/decklink_common.cpp b/libavdevice/decklink_common.cpp
index c9107c036a59c717f67abcb448e0e4e27b8f97f0..f01fba953e8ee9011a9f4dfed2d3d8f3ddfd0cd1 100644 (file)
--- a/libavdevice/decklink_common.cpp
+++ b/libavdevice/decklink_common.cpp
@@ -26,9 +26,6 @@
 #include <DeckLinkAPIDispatch.cpp>
 #endif
 
-#include <pthread.h>
-#include <semaphore.h>
-
 extern "C" {
 #include "libavformat/avformat.h"
 #include "libavformat/internal.h"

diff --git a/libavdevice/decklink_common.h b/libavdevice/decklink_common.h
index 4753287ecf79852041ea4c4d28dc56e2bfde42f9..c12cf18d70337aed815cee4903be0a0914796590 100644 (file)
--- a/libavdevice/decklink_common.h
+++ b/libavdevice/decklink_common.h
@@ -24,6 +24,7 @@
 
 #include <DeckLinkAPIVersion.h>
 
+#include "libavutil/thread.h"
 #include "decklink_common_c.h"
 
 class decklink_output_callback;
@@ -89,7 +90,9 @@ struct decklink_ctx {
     int frames_preroll;
     int frames_buffer;
 
-    sem_t semaphore;
+    pthread_mutex_t mutex;
+    pthread_cond_t cond;
+    int frames_buffer_available_spots;
 
     int channels;
 };

diff --git a/libavdevice/decklink_dec.cpp b/libavdevice/decklink_dec.cpp
index 8cc1bdf7c9dcc2275ebde6cb626993c56a4f0ef3..67eaf97e8919243784891d2eb2e331ffe5b88c76 100644 (file)
--- a/libavdevice/decklink_dec.cpp
+++ b/libavdevice/decklink_dec.cpp
@@ -21,9 +21,6 @@
 
 #include <DeckLinkAPI.h>
 
-#include <pthread.h>
-#include <semaphore.h>
-
 extern "C" {
 #include "config.h"
 #include "libavformat/avformat.h"

diff --git a/libavdevice/decklink_enc.cpp b/libavdevice/decklink_enc.cpp
index 18ef9058e28c38752b1b9c2c39cdb0a6c08c8785..51059671018862443e9b5009fb42f7bd851fced8 100644 (file)
--- a/libavdevice/decklink_enc.cpp
+++ b/libavdevice/decklink_enc.cpp
@@ -24,9 +24,6 @@ using std::atomic;
 
 #include <DeckLinkAPI.h>
 
-#include <pthread.h>
-#include <semaphore.h>
-
 extern "C" {
 #include "libavformat/avformat.h"
 #include "libavformat/internal.h"
@@ -91,7 +88,10 @@ public:
 
         av_frame_unref(avframe);
 
-        sem_post(&ctx->semaphore);
+        pthread_mutex_lock(&ctx->mutex);
+        ctx->frames_buffer_available_spots++;
+        pthread_cond_broadcast(&ctx->cond);
+        pthread_mutex_unlock(&ctx->mutex);
 
         return S_OK;
     }
@@ -133,7 +133,6 @@ static int decklink_setup_video(AVFormatContext *avctx, AVStream *st)
     ctx->output_callback = new decklink_output_callback();
     ctx->dlo->SetScheduledFrameCompletionCallback(ctx->output_callback);
 
-    /* Start video semaphore. */
     ctx->frames_preroll = st->time_base.den * ctx->preroll;
     if (st->time_base.den > 1000)
         ctx->frames_preroll /= 1000;
@@ -141,7 +140,9 @@ static int decklink_setup_video(AVFormatContext *avctx, AVStream *st)
     /* Buffer twice as many frames as the preroll. */
     ctx->frames_buffer = ctx->frames_preroll * 2;
     ctx->frames_buffer = FFMIN(ctx->frames_buffer, 60);
-    sem_init(&ctx->semaphore, 0, ctx->frames_buffer);
+    pthread_mutex_init(&ctx->mutex, NULL);
+    pthread_cond_init(&ctx->cond, NULL);
+    ctx->frames_buffer_available_spots = ctx->frames_buffer;
 
     /* The device expects the framerate to be fixed. */
     avpriv_set_pts_info(st, 64, st->time_base.num, st->time_base.den);
@@ -211,7 +212,8 @@ av_cold int ff_decklink_write_trailer(AVFormatContext *avctx)
     if (ctx->output_callback)
         delete ctx->output_callback;
 
-    sem_destroy(&ctx->semaphore);
+    pthread_mutex_destroy(&ctx->mutex);
+    pthread_cond_destroy(&ctx->cond);
 
     av_freep(&cctx->ctx);
 
@@ -247,7 +249,12 @@ static int decklink_write_video_packet(AVFormatContext *avctx, AVPacket *pkt)
     }
 
     /* Always keep at most one second of frames buffered. */
-    sem_wait(&ctx->semaphore);
+    pthread_mutex_lock(&ctx->mutex);
+    while (ctx->frames_buffer_available_spots == 0) {
+        pthread_cond_wait(&ctx->cond, &ctx->mutex);
+    }
+    ctx->frames_buffer_available_spots--;
+    pthread_mutex_unlock(&ctx->mutex);
 
     /* Schedule frame for playback. */
     hr = ctx->dlo->ScheduleVideoFrame((struct IDeckLinkVideoFrame *) frame,