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lavf/matroska: Add functions for WebM DASH Manifest

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Add functions and logic to matroskadec for use by the WebM DASH Manifest
XML Muxer. The actual muxer is added in a future patch.

Signed-off-by: Vignesh Venkatasubramanian <vigneshv@google.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
This commit is contained in:
Vignesh Venkatasubramanian 2014-07-07 12:52:37 -07:00 committed by Michael Niedermayer
parent 895e92eca0
commit 5a20656946
2 changed files with 380 additions and 0 deletions
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12
libavformat/matroska.h
View File

@ -284,4 +284,16 @@ extern const AVMetadataConv ff_mkv_metadata_conv[];
extern const char * const ff_matroska_video_stereo_mode[MATROSKA_VIDEO_STEREO_MODE_COUNT];
extern const char * const ff_matroska_video_stereo_plane[MATROSKA_VIDEO_STEREO_PLANE_COUNT];
/* AVStream Metadata tag keys for WebM Dash Manifest */
#define INITIALIZATION_RANGE "webm_dash_manifest_initialization_range"
#define CUES_START "webm_dash_manifest_cues_start"
#define CUES_END "webm_dash_manifest_cues_end"
#define FILENAME "webm_dash_manifest_file_name"
#define BANDWIDTH "webm_dash_manifest_bandwidth"
#define DURATION "webm_dash_manifest_duration"
#define CLUSTER_KEYFRAME "webm_dash_manifest_cluster_keyframe"
#define CUE_TIMESTAMPS "webm_dash_manifest_cue_timestamps"
#define TRACK_NUMBER "webm_dash_manifest_track_number"
#define CODEC_PRIVATE_SIZE "webm_dash_manifest_codec_priv_size"
#endif /* AVFORMAT_MATROSKA_H */

368
libavformat/matroskadec.c
View File

@ -3068,6 +3068,365 @@ static int matroska_read_close(AVFormatContext *s)
return 0;
}
typedef struct {
int64_t start_time_ns;
int64_t end_time_ns;
int64_t start_offset;
int64_t end_offset;
} CueDesc;
/* This function searches all the Cues and returns the CueDesc corresponding the
* the timestamp ts. Returned CueDesc will be such that start_time_ns <= ts <
* end_time_ns. All 4 fields will be set to -1 if ts >= file's duration.
*/
static CueDesc get_cue_desc(AVFormatContext *s, int64_t ts, int64_t cues_start) {
MatroskaDemuxContext *matroska = s->priv_data;
CueDesc cue_desc;
int i;
int nb_index_entries = s->streams[0]->nb_index_entries;
AVIndexEntry *index_entries = s->streams[0]->index_entries;
if (ts >= matroska->duration * matroska->time_scale) return (CueDesc) {-1, -1, -1, -1};
for (i = 1; i < nb_index_entries; i++) {
if (index_entries[i - 1].timestamp * matroska->time_scale <= ts &&
index_entries[i].timestamp * matroska->time_scale > ts) {
break;
}
}
--i;
cue_desc.start_time_ns = index_entries[i].timestamp * matroska->time_scale;
cue_desc.start_offset = index_entries[i].pos - matroska->segment_start;
if (i != nb_index_entries - 1) {
cue_desc.end_time_ns = index_entries[i + 1].timestamp * matroska->time_scale;
cue_desc.end_offset = index_entries[i + 1].pos - matroska->segment_start;
} else {
cue_desc.end_time_ns = matroska->duration * matroska->time_scale;
// FIXME: this needs special handling for files where Cues appear
// before Clusters. the current logic assumes Cues appear after
// Clusters.
cue_desc.end_offset = cues_start - matroska->segment_start;
}
return cue_desc;
}
static int webm_clusters_start_with_keyframe(AVFormatContext *s)
{
MatroskaDemuxContext *matroska = s->priv_data;
int64_t cluster_pos, before_pos;
int index, rv = 1;
if (s->streams[0]->nb_index_entries <= 0) return 0;
// seek to the first cluster using cues.
index = av_index_search_timestamp(s->streams[0], 0, 0);
if (index < 0) return 0;
cluster_pos = s->streams[0]->index_entries[index].pos;
before_pos = avio_tell(s->pb);
while (1) {
int64_t cluster_id = 0, cluster_length = 0;
AVPacket *pkt;
avio_seek(s->pb, cluster_pos, SEEK_SET);
// read cluster id and length
ebml_read_num(matroska, matroska->ctx->pb, 4, &cluster_id);
ebml_read_length(matroska, matroska->ctx->pb, &cluster_length);
if (cluster_id != 0xF43B675) { // done with all clusters
break;
}
avio_seek(s->pb, cluster_pos, SEEK_SET);
matroska->current_id = 0;
matroska_clear_queue(matroska);
if (matroska_parse_cluster(matroska) < 0 ||
matroska->num_packets <= 0) {
break;
}
pkt = matroska->packets[0];
cluster_pos += cluster_length + 12; // 12 is the offset of the cluster id and length.
if (!(pkt->flags & AV_PKT_FLAG_KEY)) {
rv = 0;
break;
}
}
avio_seek(s->pb, before_pos, SEEK_SET);
return rv;
}
static int buffer_size_after_time_downloaded(int64_t time_ns, double search_sec, int64_t bps,
double min_buffer, double* buffer,
double* sec_to_download, AVFormatContext *s,
int64_t cues_start)
{
double nano_seconds_per_second = 1000000000.0;
double time_sec = time_ns / nano_seconds_per_second;
int rv = 0;
int64_t time_to_search_ns = (int64_t)(search_sec * nano_seconds_per_second);
int64_t end_time_ns = time_ns + time_to_search_ns;
double sec_downloaded = 0.0;
CueDesc desc_curr = get_cue_desc(s, time_ns, cues_start);
if (desc_curr.start_time_ns == -1)
return -1;
*sec_to_download = 0.0;
// Check for non cue start time.
if (time_ns > desc_curr.start_time_ns) {
int64_t cue_nano = desc_curr.end_time_ns - time_ns;
double percent = (double)(cue_nano) / (desc_curr.end_time_ns - desc_curr.start_time_ns);
double cueBytes = (desc_curr.end_offset - desc_curr.start_offset) * percent;
double timeToDownload = (cueBytes * 8.0) / bps;
sec_downloaded += (cue_nano / nano_seconds_per_second) - timeToDownload;
*sec_to_download += timeToDownload;
// Check if the search ends within the first cue.
if (desc_curr.end_time_ns >= end_time_ns) {
double desc_end_time_sec = desc_curr.end_time_ns / nano_seconds_per_second;
double percent_to_sub = search_sec / (desc_end_time_sec - time_sec);
sec_downloaded = percent_to_sub * sec_downloaded;
*sec_to_download = percent_to_sub * *sec_to_download;
}
if ((sec_downloaded + *buffer) <= min_buffer) {
return 1;
}
// Get the next Cue.
desc_curr = get_cue_desc(s, desc_curr.end_time_ns, cues_start);
}
while (desc_curr.start_time_ns != -1) {
int64_t desc_bytes = desc_curr.end_offset - desc_curr.start_offset;
int64_t desc_ns = desc_curr.end_time_ns - desc_curr.start_time_ns;
double desc_sec = desc_ns / nano_seconds_per_second;
double bits = (desc_bytes * 8.0);
double time_to_download = bits / bps;
sec_downloaded += desc_sec - time_to_download;
*sec_to_download += time_to_download;
if (desc_curr.end_time_ns >= end_time_ns) {
double desc_end_time_sec = desc_curr.end_time_ns / nano_seconds_per_second;
double percent_to_sub = search_sec / (desc_end_time_sec - time_sec);
sec_downloaded = percent_to_sub * sec_downloaded;
*sec_to_download = percent_to_sub * *sec_to_download;
if ((sec_downloaded + *buffer) <= min_buffer)
rv = 1;
break;
}
if ((sec_downloaded + *buffer) <= min_buffer) {
rv = 1;
break;
}
desc_curr = get_cue_desc(s, desc_curr.end_time_ns, cues_start);
}
*buffer = *buffer + sec_downloaded;
return rv;
}
/* This function computes the bandwidth of the WebM file with the help of
* buffer_size_after_time_downloaded() function. Both of these functions are
* adapted from WebM Tools project and are adapted to work with FFmpeg's
* Matroska parsing mechanism.
*
* Returns the bandwidth of the file on success; -1 on error.
* */
static int64_t webm_dash_manifest_compute_bandwidth(AVFormatContext *s, int64_t cues_start)
{
MatroskaDemuxContext *matroska = s->priv_data;
AVStream *st = s->streams[0];
double bandwidth = 0.0;
for (int i = 0; i < st->nb_index_entries; i++) {
int64_t prebuffer_ns = 1000000000;
int64_t time_ns = st->index_entries[i].timestamp * matroska->time_scale;
double nano_seconds_per_second = 1000000000.0;
int64_t prebuffered_ns = time_ns + prebuffer_ns;
double prebuffer_bytes = 0.0;
int64_t temp_prebuffer_ns = prebuffer_ns;
int64_t pre_bytes, pre_ns;
double pre_sec, prebuffer, bits_per_second;
CueDesc desc_beg = get_cue_desc(s, time_ns, cues_start);
// Start with the first Cue.
CueDesc desc_end = desc_beg;
// Figure out how much data we have downloaded for the prebuffer. This will
// be used later to adjust the bits per sample to try.
while (desc_end.start_time_ns != -1 && desc_end.end_time_ns < prebuffered_ns) {
// Prebuffered the entire Cue.
prebuffer_bytes += desc_end.end_offset - desc_end.start_offset;
temp_prebuffer_ns -= desc_end.end_time_ns - desc_end.start_time_ns;
desc_end = get_cue_desc(s, desc_end.end_time_ns, cues_start);
}
if (desc_end.start_time_ns == -1) {
// The prebuffer is larger than the duration.
return (matroska->duration * matroska->time_scale >= prebuffered_ns) ? -1 : 0;
}
// The prebuffer ends in the last Cue. Estimate how much data was
// prebuffered.
pre_bytes = desc_end.end_offset - desc_end.start_offset;
pre_ns = desc_end.end_time_ns - desc_end.start_time_ns;
pre_sec = pre_ns / nano_seconds_per_second;
prebuffer_bytes +=
pre_bytes * ((temp_prebuffer_ns / nano_seconds_per_second) / pre_sec);
prebuffer = prebuffer_ns / nano_seconds_per_second;
// Set this to 0.0 in case our prebuffer buffers the entire video.
bits_per_second = 0.0;
do {
int64_t desc_bytes = desc_end.end_offset - desc_beg.start_offset;
int64_t desc_ns = desc_end.end_time_ns - desc_beg.start_time_ns;
double desc_sec = desc_ns / nano_seconds_per_second;
double calc_bits_per_second = (desc_bytes * 8) / desc_sec;
// Drop the bps by the percentage of bytes buffered.
double percent = (desc_bytes - prebuffer_bytes) / desc_bytes;
double mod_bits_per_second = calc_bits_per_second * percent;
if (prebuffer < desc_sec) {
double search_sec =
(double)(matroska->duration * matroska->time_scale) / nano_seconds_per_second;
// Add 1 so the bits per second should be a little bit greater than file
// datarate.
int64_t bps = (int64_t)(mod_bits_per_second) + 1;
const double min_buffer = 0.0;
double buffer = prebuffer;
double sec_to_download = 0.0;
int rv = buffer_size_after_time_downloaded(prebuffered_ns, search_sec, bps,
min_buffer, &buffer, &sec_to_download,
s, cues_start);
if (rv < 0) {
return -1;
} else if (rv == 0) {
bits_per_second = (double)(bps);
break;
}
}
desc_end = get_cue_desc(s, desc_end.end_time_ns, cues_start);
} while (desc_end.start_time_ns != -1);
if (bandwidth < bits_per_second) bandwidth = bits_per_second;
}
return (int64_t)bandwidth;
}
static int webm_dash_manifest_cues(AVFormatContext *s)
{
MatroskaDemuxContext *matroska = s->priv_data;
EbmlList *seekhead_list = &matroska->seekhead;
MatroskaSeekhead *seekhead = seekhead_list->elem;
char *buf;
int64_t cues_start, cues_end, before_pos, bandwidth;
int i;
// determine cues start and end positions
for (i = 0; i < seekhead_list->nb_elem; i++)
if (seekhead[i].id == MATROSKA_ID_CUES)
break;
if (i >= seekhead_list->nb_elem) return -1;
before_pos = avio_tell(matroska->ctx->pb);
cues_start = seekhead[i].pos + matroska->segment_start;
if (avio_seek(matroska->ctx->pb, cues_start, SEEK_SET) == cues_start) {
uint64_t cues_length = 0, cues_id = 0;
ebml_read_num(matroska, matroska->ctx->pb, 4, &cues_id);
ebml_read_length(matroska, matroska->ctx->pb, &cues_length);
cues_end = cues_start + cues_length + 11; // 11 is the offset of Cues ID.
}
avio_seek(matroska->ctx->pb, before_pos, SEEK_SET);
// parse the cues
matroska_parse_cues(matroska);
// cues start
buf = av_asprintf("%" PRId64, cues_start);
if (!buf) return AVERROR(ENOMEM);
av_dict_set(&s->streams[0]->metadata, CUES_START, buf, 0);
av_free(buf);
// cues end
buf = av_asprintf("%" PRId64, cues_end);
if (!buf) return AVERROR(ENOMEM);
av_dict_set(&s->streams[0]->metadata, CUES_END, buf, 0);
av_free(buf);
// bandwidth
bandwidth = webm_dash_manifest_compute_bandwidth(s, cues_start);
if (bandwidth < 0) return -1;
buf = av_asprintf("%" PRId64, bandwidth);
if (!buf) return AVERROR(ENOMEM);
av_dict_set(&s->streams[0]->metadata, BANDWIDTH, buf, 0);
av_free(buf);
// check if all clusters start with key frames
buf = av_asprintf("%d", webm_clusters_start_with_keyframe(s));
if (!buf) return AVERROR(ENOMEM);
av_dict_set(&s->streams[0]->metadata, CLUSTER_KEYFRAME, buf, 0);
av_free(buf);
// store cue point timestamps as a comma separated list for checking subsegment alignment in
// the muxer. assumes that each timestamp cannot be more than 20 characters long.
buf = av_malloc(s->streams[0]->nb_index_entries * 20 * sizeof(char));
if (!buf) return -1;
strcpy(buf, "");
for (i = 0; i < s->streams[0]->nb_index_entries; i++) {
snprintf(buf, (i + 1) * 20 * sizeof(char),
"%s%" PRId64, buf, s->streams[0]->index_entries[i].timestamp);
if (i != s->streams[0]->nb_index_entries - 1)
strncat(buf, ",", sizeof(char));
}
av_dict_set(&s->streams[0]->metadata, CUE_TIMESTAMPS, buf, 0);
av_free(buf);
return 0;
}
static int webm_dash_manifest_read_header(AVFormatContext *s)
{
char *buf;
int ret = matroska_read_header(s);
MatroskaTrack *tracks;
MatroskaDemuxContext *matroska = s->priv_data;
if (ret) {
av_log(s, AV_LOG_ERROR, "Failed to read file headers\n");
return -1;
}
// initialization range
buf = av_asprintf("%" PRId64, avio_tell(s->pb) - 5); // 5 is the offset of Cluster ID.
if (!buf) return AVERROR(ENOMEM);
av_dict_set(&s->streams[0]->metadata, INITIALIZATION_RANGE, buf, 0);
av_free(buf);
// basename of the file
buf = strrchr(s->filename, '/');
if (buf == NULL) return -1;
av_dict_set(&s->streams[0]->metadata, FILENAME, ++buf, 0);
// duration
buf = av_asprintf("%g", matroska->duration);
if (!buf) return AVERROR(ENOMEM);
av_dict_set(&s->streams[0]->metadata, DURATION, buf, 0);
av_free(buf);
// track number
tracks = matroska->tracks.elem;
buf = av_asprintf("%" PRId64, tracks[0].num);
if (!buf) return AVERROR(ENOMEM);
av_dict_set(&s->streams[0]->metadata, TRACK_NUMBER, buf, 0);
av_free(buf);
// parse the cues and populate Cue related fields
return webm_dash_manifest_cues(s);
}
static int webm_dash_manifest_read_packet(AVFormatContext *s, AVPacket *pkt)
{
return AVERROR_EOF;
}
AVInputFormat ff_matroska_demuxer = {
.name = "matroska,webm",
.long_name = NULL_IF_CONFIG_SMALL("Matroska / WebM"),
@ -3078,3 +3437,12 @@ AVInputFormat ff_matroska_demuxer = {
.read_close = matroska_read_close,
.read_seek = matroska_read_seek,
};
AVInputFormat ff_webm_dash_manifest_demuxer = {
.name = "webm_dash_manifest",
.long_name = NULL_IF_CONFIG_SMALL("WebM DASH Manifest"),
.priv_data_size = sizeof(MatroskaDemuxContext),
.read_header = webm_dash_manifest_read_header,
.read_packet = webm_dash_manifest_read_packet,
.read_close = matroska_read_close,
};