On 4/20/2021 1:01 AM, Brad Hards wrote:
This adds support for the EventMessage box, which is apparently described in
ISO/IEC 23009-1:2019, and is used for KLV metadata per MISB ST 1910.
See https://www.gwg.nga.mil/misb/docs/standards/ST1910.1.pdf Sect 6.2.1
---
libavformat/isom.h | 15 ++++++++++++
libavformat/mov.c | 61 ++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 76 insertions(+)
diff --git a/libavformat/isom.h b/libavformat/isom.h
index 5a6d504090..8ea62e91f0 100644
--- a/libavformat/isom.h
+++ b/libavformat/isom.h
@@ -79,6 +79,18 @@ typedef struct MOVDref {
int16_t nlvl_to, nlvl_from;
} MOVDref;
+typedef struct MOVEmsg {
+ uint8_t version;
+ uint32_t timescale;
+ uint32_t presentation_time_delta; ///< only valid for version 0
+ uint64_t presentation_time; ///< only valid for version 1
+ uint32_t event_duration;
+ uint32_t id;
+ char *scheme_id_uri;
+ char *value;
+ uint8_t *message_data;
+} MOVEmsg;
+
typedef struct MOVAtom {
uint32_t type;
int64_t size; /* total size (excluding the size and type fields) */
@@ -297,6 +309,9 @@ typedef struct MOVContext {
int32_t movie_display_matrix[3][3]; ///< display matrix from mvhd
int have_read_mfra_size;
uint32_t mfra_size;
+ // Event Messages from DASH specification, used in MISB ST 1910
+ unsigned emsg_count; ///< Number of event messages
+ MOVEmsg *emsg_data; ///< Array of Event Messages
You're not freeing this array anywhere. Same with each entry's
message_data, scheme_id_uri and value.
} MOVContext;
int ff_mp4_read_descr_len(AVIOContext *pb);
diff --git a/libavformat/mov.c b/libavformat/mov.c
index 7805330bf9..22bf0b36ea 100644
--- a/libavformat/mov.c
+++ b/libavformat/mov.c
@@ -5318,6 +5318,66 @@ static int mov_read_elst(MOVContext *c, AVIOContext *pb,
MOVAtom atom)
return 0;
}
+static int mov_read_emsg(MOVContext *c, AVIOContext *pb, MOVAtom atom)
+{
+ int err;
+ uint32_t bytes_read_from_atom = 0;
+ size_t num_bytes_in_last_read;
+ MOVEmsg *emsg;
+
+ if ((uint64_t)c->emsg_count+1 >= UINT_MAX / sizeof(*c->emsg_data))
+ return AVERROR_INVALIDDATA;
+ if ((err = av_reallocp_array(&c->emsg_data, c->emsg_count + 1,
If there can be several emsg atoms in a bitstream, it may be a better
idea to use av_fast_realloc() instead.
Also, no limit to their lifetime? Being events, one would expect they
could be dropped after being handled.
+ sizeof(*c->emsg_data))) < 0) {
+ c->emsg_count = 0;
+ return err;
+ }
+ emsg = &c->emsg_data[c->emsg_count++];
+
+ emsg->version = avio_r8(pb);
+ bytes_read_from_atom += 1;
+ avio_rb24(pb); /* flags */
+ bytes_read_from_atom += 3;
+ if (emsg->version == 0) {
+ emsg->scheme_id_uri = av_malloc(atom.size + 1);
+ num_bytes_in_last_read = avio_get_str(pb, atom.size, emsg->scheme_id_uri,
pb->buffer_size + 1);
+ bytes_read_from_atom += num_bytes_in_last_read;
+ av_realloc(emsg->scheme_id_uri, num_bytes_in_last_read);
+ emsg->value = av_malloc(atom.size + 1);
+ num_bytes_in_last_read = avio_get_str(pb, atom.size, emsg->value,
pb->buffer_size + 1);
+ bytes_read_from_atom += num_bytes_in_last_read;
+ av_realloc(emsg->value, num_bytes_in_last_read);
+ emsg->timescale = avio_rb32(pb);
+ bytes_read_from_atom += 4;
+ emsg->presentation_time_delta = avio_rb32(pb);
+ bytes_read_from_atom += 4;
+ emsg->event_duration = avio_rb32(pb);
+ bytes_read_from_atom += 4;
+ emsg->id = avio_rb32(pb);
+ bytes_read_from_atom += 4;
+ } else if (emsg->version == 1) {
+ emsg->timescale = avio_rb32(pb);
+ bytes_read_from_atom += 4;
+ emsg->presentation_time = avio_rb64(pb);
+ bytes_read_from_atom += 8;
+ emsg->event_duration = avio_rb32(pb);
+ bytes_read_from_atom += 4;
+ emsg->id = avio_rb32(pb);
+ bytes_read_from_atom += 4;
+ emsg->scheme_id_uri = av_malloc(atom.size + 1);
+ num_bytes_in_last_read = avio_get_str(pb, atom.size, emsg->scheme_id_uri,
pb->buffer_size + 1);
+ bytes_read_from_atom += num_bytes_in_last_read;
+ av_realloc(emsg->scheme_id_uri, num_bytes_in_last_read);
+ emsg->value = av_malloc(atom.size + 1);
+ num_bytes_in_last_read = avio_get_str(pb, atom.size, emsg->value,
pb->buffer_size + 1);
+ bytes_read_from_atom += num_bytes_in_last_read;
Use avio_tell() instead of keeping a byte count with this
bytes_read_from_atom variable. As is this is pretty unreadable.
+ av_realloc(emsg->value, num_bytes_in_last_read);
+ }
+ emsg->message_data = av_malloc(atom.size - bytes_read_from_atom);
+ num_bytes_in_last_read = avio_read(pb, emsg->message_data, atom.size -
bytes_read_from_atom);
+ return 0;
You're not doing anything with these event messages. You're only storing
them in an ever growing array.
+}
+
static int mov_read_tmcd(MOVContext *c, AVIOContext *pb, MOVAtom atom)
{
MOVStreamContext *sc;
@@ -6895,6 +6955,7 @@ static const MOVParseTableEntry mov_default_parse_table[]
= {
{ MKTAG('d','r','e','f'), mov_read_dref },
{ MKTAG('e','d','t','s'), mov_read_default },
{ MKTAG('e','l','s','t'), mov_read_elst },
+{ MKTAG('e','m','s','g'), mov_read_emsg },
{ MKTAG('e','n','d','a'), mov_read_enda },
{ MKTAG('f','i','e','l'), mov_read_fiel },
{ MKTAG('a','d','r','m'), mov_read_adrm },
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