From: Tomas Härdin <[email protected]>
---
libavformat/mxfdec.c | 69 ++++++++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 69 insertions(+), 0 deletions(-)
diff --git a/libavformat/mxfdec.c b/libavformat/mxfdec.c
index 95e54c7..8402165 100644
--- a/libavformat/mxfdec.c
+++ b/libavformat/mxfdec.c
@@ -79,6 +79,8 @@ typedef struct {
int index_sid;
int body_sid;
int64_t this_partition;
+ int64_t essence_offset; /* absolute offset of essence */
+ int64_t essence_length;
} MXFPartition;
typedef struct {
@@ -1424,6 +1426,46 @@ static int mxf_parse_handle_partition_or_eof(MXFContext
*mxf)
return mxf->parsing_backward ? mxf_seek_to_previous_partition(mxf) : 1;
}
+/**
+ * Figures out the proper offset and length of the essence container in each
partition
+ */
+static void mxf_compute_essence_containers(MXFContext *mxf)
+{
+ int x;
+
+ /* everything is already correct */
+ if (mxf->op == OPAtom)
+ return;
+
+ for (x = 0; x < mxf->partitions_count; x++) {
+ MXFPartition *p = &mxf->partitions[x];
+
+ if (!p->body_sid)
+ continue; /* BodySID == 0 -> no essence */
+
+ if (x >= mxf->partitions_count - 1)
+ break; /* last partition - can't compute length (and we
don't need to) */
+
+ /* essence container spans to the next partition */
+ p->essence_length = mxf->partitions[x+1].this_partition -
p->essence_offset;
+
+ if (p->essence_length < 0) {
+ /* next ThisPartition < essence_offset */
+ p->essence_length = 0;
+ av_log(mxf->fc, AV_LOG_ERROR, "partition %i: bad ThisPartition =
%lx\n",
+ x+1, mxf->partitions[x+1].this_partition);
+ }
+ }
+}
+
+static int64_t round_to_kag(int64_t position, int kag_size)
+{
+ /* TODO: account for run-in? the spec isn't clear whether KAG should
account for it */
+ /* NOTE: kag_size may be any integer between 1 - 2^10 */
+ int64_t ret = (position / kag_size) * kag_size;
+ return ret == position ? ret : ret + kag_size;
+}
+
static int mxf_read_header(AVFormatContext *s, AVFormatParameters *ap)
{
MXFContext *mxf = s->priv_data;
@@ -1455,6 +1497,30 @@ static int mxf_read_header(AVFormatContext *s,
AVFormatParameters *ap)
if (IS_KLV_KEY(klv.key, mxf_encrypted_triplet_key) ||
IS_KLV_KEY(klv.key, mxf_essence_element_key) ||
IS_KLV_KEY(klv.key, mxf_system_item_key)) {
+ if (!mxf->current_partition->essence_offset) {
+ /* for OP1a we compute essence_offset
+ * for OPAtom we point essence_offset after the KL (usually
op1a_essence_offset + 20 or 25)
+ * TODO: for OP1a we could eliminate this entire if statement,
always stopping parsing at op1a_essence_offset
+ * for OPAtom we still need the actual essence_offset
though (the KL's length can vary)
+ */
+ int64_t op1a_essence_offset =
+ round_to_kag(mxf->current_partition->this_partition +
+ mxf->current_partition->pack_length,
mxf->current_partition->kag_size) +
+ round_to_kag(mxf->current_partition->header_byte_count,
mxf->current_partition->kag_size) +
+ round_to_kag(mxf->current_partition->index_byte_count,
mxf->current_partition->kag_size);
+
+ if (mxf->op == OPAtom) {
+ /* point essence_offset to the actual data
+ * OPAtom has all the essence in one big KLV
+ */
+ mxf->current_partition->essence_offset = avio_tell(s->pb);
+ mxf->current_partition->essence_length = klv.length;
+ } else {
+ /* NOTE: op1a_essence_offset may be less than to
klv.offset (C0023S01.mxf) */
+ mxf->current_partition->essence_offset =
op1a_essence_offset;
+ }
+ }
+
if (IS_KLV_KEY(klv.key, mxf_system_item_key)) {
mxf->system_item = 1;
}
@@ -1504,6 +1570,9 @@ static int mxf_read_header(AVFormatContext *s,
AVFormatParameters *ap)
return AVERROR_INVALIDDATA;
}
avio_seek(s->pb, mxf->essence_offset, SEEK_SET);
+
+ mxf_compute_essence_containers(mxf);
+
return mxf_parse_structural_metadata(mxf);
}
--
1.7.8
_______________________________________________
libav-devel mailing list
[email protected]
https://lists.libav.org/mailman/listinfo/libav-devel
