avcodec/bsf: Add ff_bsf_get_packet_ref() function

Use of this function can save unnecessary malloc operation
in bitstream filter.

Signed-off-by: Jan Sebechlebsky <sebechlebskyjan@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
Signed-off-by: Luca Barbato <lu_zero@gentoo.org>

libavcodec/bsf.c

@@ -227,3 +227,19 @@ int ff_bsf_get_packet(AVBSFContext *ctx, AVPacket **pkt)
 
     return 0;
 }
+
+int ff_bsf_get_packet_ref(AVBSFContext *ctx, AVPacket *pkt)
+{
+    AVBSFInternal *in = ctx->internal;
+
+    if (in->eof)
+        return AVERROR_EOF;
+
+    if (!ctx->internal->buffer_pkt->data &&
+        !ctx->internal->buffer_pkt->side_data_elems)
+        return AVERROR(EAGAIN);
+
+    av_packet_move_ref(pkt, ctx->internal->buffer_pkt);
+
+    return 0;
+}

libavcodec/bsf.h

@@ -28,6 +28,17 @@
  */
 int ff_bsf_get_packet(AVBSFContext *ctx, AVPacket **pkt);
 
+/**
+ * Called by bitstream filters to get packet for filtering.
+ * The reference to packet is moved to provided packet structure.
+ *
+ * @param ctx pointer to AVBSFContext of filter
+ * @param pkt pointer to packet to move reference to
+ *
+ * @return 0>= on success, negative AVERROR in case of failure
+ */
+int ff_bsf_get_packet_ref(AVBSFContext *ctx, AVPacket *pkt);
+
 const AVClass *ff_bsf_child_class_next(const AVClass *prev);
 
 #endif /* AVCODEC_BSF_H */