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Code

Probe SimpleBlocks to determine which clusters start with a keyframe.

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This commit is contained in:
Joseph Wallace 2015-11-21 03:29:56 -05:00
parent 6e11db5de2
commit 9cf4ed560c
1 changed files with 54 additions and 3 deletions
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57
src/format_ebml.c
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@ -61,6 +61,12 @@ typedef enum ebml_chunk_type {
EBML_CHUNK_CLUSTER_CONTINUE
} ebml_chunk_type;
typedef enum ebml_keyframe_status {
EBML_KEYFRAME_UNKNOWN = -1,
EBML_KEYFRAME_DOES_NOT_START_CLUSTER = 0,
EBML_KEYFRAME_STARTS_CLUSTER = 1
} ebml_keyframe_status;
typedef struct ebml_client_data_st ebml_client_data_t;
struct ebml_client_data_st {
@ -77,6 +83,7 @@ struct ebml_st {
unsigned long long copy_len;
int cluster_start;
ebml_keyframe_status cluster_starts_with_keyframe;
int flush_cluster;
int position;
@ -473,7 +480,11 @@ static int ebml_read(ebml_t *ebml, char *buffer, int len, ebml_chunk_type *chunk
if (ebml->cluster_start == 0) {
/* new cluster is starting now */
*chunk_type = EBML_CHUNK_CLUSTER_START;
if (ebml->cluster_starts_with_keyframe == EBML_KEYFRAME_STARTS_CLUSTER) {
/* Successfully found a keyframe in this cluster's video track */
*chunk_type = EBML_CHUNK_CLUSTER_START;
}
/* mark end of cluster */
ebml->cluster_start = -1;
@ -531,8 +542,11 @@ static int ebml_wrote(ebml_t *ebml, int len)
int tag_length;
int value_length;
int track_number_length;
unsigned long long payload_length;
unsigned long long data_value;
unsigned long long track_number;
unsigned char flags;
int copy_state;
char *segment_id = "\x18\x53\x80\x67";
@ -541,6 +555,7 @@ static int ebml_wrote(ebml_t *ebml, int len)
char *track_entry_id = "\xAE";
char *track_number_id = "\xD7";
char *track_type_id = "\x83";
char *simple_block_id = "\xA3";
ebml->input_position += len;
end_of_buffer = ebml->input_buffer + ebml->input_position;
@ -585,7 +600,42 @@ static int ebml_wrote(ebml_t *ebml, int len)
}
if (tag_length > 1) {
if (!memcmp(ebml->input_buffer + cursor, track_entry_id, 1)) {
if (!memcmp(ebml->input_buffer + cursor, simple_block_id, 1)) {
/* Probe SimpleBlock header for the keyframe status */
if (ebml->cluster_starts_with_keyframe == EBML_KEYFRAME_UNKNOWN) {
track_number_length = ebml_parse_var_int(ebml->input_buffer + cursor + tag_length,
end_of_buffer, &track_number);
if (track_number_length == 0) {
/* Wait for more data */
processing = 0;
} else if (track_number_length < 0) {
return -1;
} else if (track_number == ebml->keyframe_track_number) {
/* this block belongs to the video track */
/* skip the 16-bit timecode for now, read the flags byte */
if (cursor + tag_length + track_number_length + 2 >= ebml->input_position) {
/* Wait for more data */
processing = 0;
} else {
flags = ebml->input_buffer[cursor + tag_length + track_number_length + 2];
if (flags & 0x80) {
/* "keyframe" flag is set */
ebml->cluster_starts_with_keyframe = EBML_KEYFRAME_STARTS_CLUSTER;
/* ICECAST_LOG_DEBUG("Found keyframe in track %hhu", track_number); */
} else {
ebml->cluster_starts_with_keyframe = EBML_KEYFRAME_DOES_NOT_START_CLUSTER;
/* ICECAST_LOG_DEBUG("Found non-keyframe in track %hhu", track_number); */
}
}
}
}
} else if (!memcmp(ebml->input_buffer + cursor, track_entry_id, 1)) {
/* Parse all TrackEntry children; reset the state */
payload_length = 0;
ebml->parsing_track_number = EBML_UNKNOWN;
@ -668,8 +718,9 @@ static int ebml_wrote(ebml_t *ebml, int len)
/* The header has been fully read by now, publish its size. */
ebml->header_size = ebml->header_position;
/* Mark this sync point */
/* Mark this potential sync point, prepare probe */
ebml->cluster_start = ebml->position;
ebml->cluster_starts_with_keyframe = EBML_KEYFRAME_UNKNOWN;
/* Buffer data to give us time to probe for keyframes, etc. */
ebml->flush_cluster = 0;