Commit dc263858 authored by Joseph Wallace's avatar Joseph Wallace

Additional format_ebml.c comments.

parent af238d91
......@@ -36,7 +36,17 @@
#include "logging.h"
/* The size of the header buffer; should be large enough to contain
* everything before the first Cluster in a reasonable stream
*/
#define EBML_HEADER_MAX_SIZE 131072
/* The size of the input/staging buffers; this much of a cluster
* will be buffered before being returned. Should be large enough
* that the first video block will be encountered before it is full,
* to allow probing for the keyframe flag while we still have the
* option to mark the cluster as a sync point.
*/
#define EBML_SLICE_SIZE 4096
/* A value that no EBML var-int is allowed to take. */
......@@ -63,28 +73,55 @@
#define TRACK_TYPE_MAGIC "\x83"
#define SIMPLE_BLOCK_MAGIC "\xA3"
/* If support for Tags gets added, it may make sense
* to convert this into a pair of flags signaling
* "new headers" and "new tags"
*/
typedef enum ebml_read_mode {
/* The header buffer has not been extracted yet */
EBML_STATE_READING_HEADER = 0,
/* The header buffer has been read, begin normal operation */
EBML_STATE_READING_CLUSTERS
} ebml_read_mode;
typedef enum ebml_parsing_state {
/* Examine EBML elements, output to header buffer */
EBML_STATE_PARSING_HEADER = 0,
/* Blindly copy a specified number of bytes to the header buffer */
EBML_STATE_COPYING_TO_HEADER,
/* Finalize header buffer and wait for previous cluster to flush (as necessary) */
EBML_STATE_START_CLUSTER,
/* Examine EBML elements, output to data buffer */
EBML_STATE_PARSING_CLUSTERS,
/* Blindly copy a specified number of bytes to the data buffer */
EBML_STATE_COPYING_TO_DATA
} ebml_parsing_state;
typedef enum ebml_chunk_type {
/* This chunk is the header buffer */
EBML_CHUNK_HEADER = 0,
/* This chunk starts a cluster that works as a sync point */
EBML_CHUNK_CLUSTER_START,
/* This chunk continues the previous cluster, or
* else starts a non-sync-point cluster
*/
EBML_CHUNK_CLUSTER_CONTINUE
} ebml_chunk_type;
typedef enum ebml_keyframe_status {
/* Have not found a video track block yet */
EBML_KEYFRAME_UNKNOWN = -1,
/* Found the first video track block, it was not a keyframe */
EBML_KEYFRAME_DOES_NOT_START_CLUSTER = 0,
/* Found the first video track block, it was a keyframe */
EBML_KEYFRAME_STARTS_CLUSTER = 1
} ebml_keyframe_status;
......@@ -695,9 +732,8 @@ static int ebml_wrote(ebml_t *ebml, int len)
}
}
/* Copy any data we don't need to probe any more */
if (processing) {
/* Non-cluster tag, copy it & children into buffer */
/* Moving to next element, copy current to buffer */
ebml->copy_len = tag_length + payload_length;
ebml->parse_state = copy_state;
}
......
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