lavc: do not implicitly share the frame pool between threads

Currently the frame pool used by the default get_buffer2()
implementation is a single struct, allocated when opening the decoder.
A pointer to it is simply copied to each frame thread and we assume that
no thread attempts to modify it at an unexpected time. This is rather
fragile and potentially dangerous.

With this commit, the frame pool is made refcounted, with the reference
being propagated across threads along with other context variables. The
frame pool is now also immutable - when the stream parameters change we
drop the old reference and create a new one.

1 files changed, 1 insertions, 20 deletions

diff --git a/libavcodec/internal.h b/libavcodec/internal.h
index 700807cd75..721fd017d4 100644
--- a/libavcodec/internal.h
+++ b/libavcodec/internal.h
@@ -108,25 +108,6 @@
 #   define STRIDE_ALIGN 8
 #endif
 
-typedef struct FramePool {
-    /**
-     * Pools for each data plane. For audio all the planes have the same size,
-     * so only pools[0] is used.
-     */
-    AVBufferPool *pools[4];
-
-    /*
-     * Pool parameters
-     */
-    int format;
-    int width, height;
-    int stride_align[AV_NUM_DATA_POINTERS];
-    int linesize[4];
-    int planes;
-    int channels;
-    int samples;
-} FramePool;
-
 typedef struct DecodeSimpleContext {
     AVPacket *in_pkt;
     AVFrame  *out_frame;
@@ -154,7 +135,7 @@ typedef struct AVCodecInternal {
 
     AVFrame *to_free;
 
-    FramePool *pool;
+    AVBufferRef *pool;
 
     void *thread_ctx;