lavf/matroska: Add functions for WebM DASH Manifest
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
Michael Niedermayer
parent
895e92eca0
commit
5a20656946
@ -284,4 +284,16 @@ extern const AVMetadataConv ff_mkv_metadata_conv[];
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extern const char * const ff_matroska_video_stereo_mode[MATROSKA_VIDEO_STEREO_MODE_COUNT];
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extern const char * const ff_matroska_video_stereo_plane[MATROSKA_VIDEO_STEREO_PLANE_COUNT];
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/* AVStream Metadata tag keys for WebM Dash Manifest */
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#define INITIALIZATION_RANGE "webm_dash_manifest_initialization_range"
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#define CUES_START "webm_dash_manifest_cues_start"
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#define CUES_END "webm_dash_manifest_cues_end"
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#define FILENAME "webm_dash_manifest_file_name"
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#define BANDWIDTH "webm_dash_manifest_bandwidth"
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#define DURATION "webm_dash_manifest_duration"
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#define CLUSTER_KEYFRAME "webm_dash_manifest_cluster_keyframe"
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#define CUE_TIMESTAMPS "webm_dash_manifest_cue_timestamps"
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#define TRACK_NUMBER "webm_dash_manifest_track_number"
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#define CODEC_PRIVATE_SIZE "webm_dash_manifest_codec_priv_size"
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#endif /* AVFORMAT_MATROSKA_H */
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@ -3068,6 +3068,365 @@ static int matroska_read_close(AVFormatContext *s)
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return 0;
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}
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typedef struct {
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int64_t start_time_ns;
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int64_t end_time_ns;
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int64_t start_offset;
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int64_t end_offset;
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} CueDesc;
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/* This function searches all the Cues and returns the CueDesc corresponding the
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* the timestamp ts. Returned CueDesc will be such that start_time_ns <= ts <
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* end_time_ns. All 4 fields will be set to -1 if ts >= file's duration.
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*/
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static CueDesc get_cue_desc(AVFormatContext *s, int64_t ts, int64_t cues_start) {
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MatroskaDemuxContext *matroska = s->priv_data;
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CueDesc cue_desc;
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int i;
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int nb_index_entries = s->streams[0]->nb_index_entries;
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AVIndexEntry *index_entries = s->streams[0]->index_entries;
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if (ts >= matroska->duration * matroska->time_scale) return (CueDesc) {-1, -1, -1, -1};
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for (i = 1; i < nb_index_entries; i++) {
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if (index_entries[i - 1].timestamp * matroska->time_scale <= ts &&
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index_entries[i].timestamp * matroska->time_scale > ts) {
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break;
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}
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}
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--i;
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cue_desc.start_time_ns = index_entries[i].timestamp * matroska->time_scale;
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cue_desc.start_offset = index_entries[i].pos - matroska->segment_start;
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if (i != nb_index_entries - 1) {
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cue_desc.end_time_ns = index_entries[i + 1].timestamp * matroska->time_scale;
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cue_desc.end_offset = index_entries[i + 1].pos - matroska->segment_start;
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} else {
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cue_desc.end_time_ns = matroska->duration * matroska->time_scale;
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// FIXME: this needs special handling for files where Cues appear
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// before Clusters. the current logic assumes Cues appear after
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// Clusters.
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cue_desc.end_offset = cues_start - matroska->segment_start;
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}
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return cue_desc;
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}
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static int webm_clusters_start_with_keyframe(AVFormatContext *s)
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{
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MatroskaDemuxContext *matroska = s->priv_data;
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int64_t cluster_pos, before_pos;
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int index, rv = 1;
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if (s->streams[0]->nb_index_entries <= 0) return 0;
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// seek to the first cluster using cues.
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index = av_index_search_timestamp(s->streams[0], 0, 0);
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if (index < 0) return 0;
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cluster_pos = s->streams[0]->index_entries[index].pos;
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before_pos = avio_tell(s->pb);
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while (1) {
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int64_t cluster_id = 0, cluster_length = 0;
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AVPacket *pkt;
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avio_seek(s->pb, cluster_pos, SEEK_SET);
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// read cluster id and length
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ebml_read_num(matroska, matroska->ctx->pb, 4, &cluster_id);
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ebml_read_length(matroska, matroska->ctx->pb, &cluster_length);
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if (cluster_id != 0xF43B675) { // done with all clusters
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break;
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}
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avio_seek(s->pb, cluster_pos, SEEK_SET);
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matroska->current_id = 0;
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matroska_clear_queue(matroska);
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if (matroska_parse_cluster(matroska) < 0 ||
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matroska->num_packets <= 0) {
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break;
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}
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pkt = matroska->packets[0];
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cluster_pos += cluster_length + 12; // 12 is the offset of the cluster id and length.
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if (!(pkt->flags & AV_PKT_FLAG_KEY)) {
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rv = 0;
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break;
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}
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}
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avio_seek(s->pb, before_pos, SEEK_SET);
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return rv;
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}
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static int buffer_size_after_time_downloaded(int64_t time_ns, double search_sec, int64_t bps,
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double min_buffer, double* buffer,
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double* sec_to_download, AVFormatContext *s,
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int64_t cues_start)
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{
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double nano_seconds_per_second = 1000000000.0;
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double time_sec = time_ns / nano_seconds_per_second;
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int rv = 0;
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int64_t time_to_search_ns = (int64_t)(search_sec * nano_seconds_per_second);
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int64_t end_time_ns = time_ns + time_to_search_ns;
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double sec_downloaded = 0.0;
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CueDesc desc_curr = get_cue_desc(s, time_ns, cues_start);
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if (desc_curr.start_time_ns == -1)
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return -1;
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*sec_to_download = 0.0;
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// Check for non cue start time.
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if (time_ns > desc_curr.start_time_ns) {
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int64_t cue_nano = desc_curr.end_time_ns - time_ns;
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double percent = (double)(cue_nano) / (desc_curr.end_time_ns - desc_curr.start_time_ns);
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double cueBytes = (desc_curr.end_offset - desc_curr.start_offset) * percent;
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double timeToDownload = (cueBytes * 8.0) / bps;
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sec_downloaded += (cue_nano / nano_seconds_per_second) - timeToDownload;
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*sec_to_download += timeToDownload;
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// Check if the search ends within the first cue.
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if (desc_curr.end_time_ns >= end_time_ns) {
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double desc_end_time_sec = desc_curr.end_time_ns / nano_seconds_per_second;
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double percent_to_sub = search_sec / (desc_end_time_sec - time_sec);
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sec_downloaded = percent_to_sub * sec_downloaded;
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*sec_to_download = percent_to_sub * *sec_to_download;
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}
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if ((sec_downloaded + *buffer) <= min_buffer) {
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return 1;
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}
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// Get the next Cue.
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desc_curr = get_cue_desc(s, desc_curr.end_time_ns, cues_start);
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}
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while (desc_curr.start_time_ns != -1) {
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int64_t desc_bytes = desc_curr.end_offset - desc_curr.start_offset;
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int64_t desc_ns = desc_curr.end_time_ns - desc_curr.start_time_ns;
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double desc_sec = desc_ns / nano_seconds_per_second;
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double bits = (desc_bytes * 8.0);
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double time_to_download = bits / bps;
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sec_downloaded += desc_sec - time_to_download;
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*sec_to_download += time_to_download;
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if (desc_curr.end_time_ns >= end_time_ns) {
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double desc_end_time_sec = desc_curr.end_time_ns / nano_seconds_per_second;
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double percent_to_sub = search_sec / (desc_end_time_sec - time_sec);
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sec_downloaded = percent_to_sub * sec_downloaded;
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*sec_to_download = percent_to_sub * *sec_to_download;
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if ((sec_downloaded + *buffer) <= min_buffer)
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rv = 1;
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break;
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}
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if ((sec_downloaded + *buffer) <= min_buffer) {
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rv = 1;
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break;
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}
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desc_curr = get_cue_desc(s, desc_curr.end_time_ns, cues_start);
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}
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*buffer = *buffer + sec_downloaded;
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return rv;
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}
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/* This function computes the bandwidth of the WebM file with the help of
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* buffer_size_after_time_downloaded() function. Both of these functions are
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* adapted from WebM Tools project and are adapted to work with FFmpeg's
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* Matroska parsing mechanism.
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*
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* Returns the bandwidth of the file on success; -1 on error.
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* */
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static int64_t webm_dash_manifest_compute_bandwidth(AVFormatContext *s, int64_t cues_start)
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{
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MatroskaDemuxContext *matroska = s->priv_data;
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AVStream *st = s->streams[0];
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double bandwidth = 0.0;
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for (int i = 0; i < st->nb_index_entries; i++) {
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int64_t prebuffer_ns = 1000000000;
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int64_t time_ns = st->index_entries[i].timestamp * matroska->time_scale;
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double nano_seconds_per_second = 1000000000.0;
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int64_t prebuffered_ns = time_ns + prebuffer_ns;
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double prebuffer_bytes = 0.0;
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int64_t temp_prebuffer_ns = prebuffer_ns;
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int64_t pre_bytes, pre_ns;
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double pre_sec, prebuffer, bits_per_second;
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CueDesc desc_beg = get_cue_desc(s, time_ns, cues_start);
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// Start with the first Cue.
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CueDesc desc_end = desc_beg;
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// Figure out how much data we have downloaded for the prebuffer. This will
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// be used later to adjust the bits per sample to try.
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while (desc_end.start_time_ns != -1 && desc_end.end_time_ns < prebuffered_ns) {
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// Prebuffered the entire Cue.
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prebuffer_bytes += desc_end.end_offset - desc_end.start_offset;
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temp_prebuffer_ns -= desc_end.end_time_ns - desc_end.start_time_ns;
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desc_end = get_cue_desc(s, desc_end.end_time_ns, cues_start);
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}
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if (desc_end.start_time_ns == -1) {
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// The prebuffer is larger than the duration.
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return (matroska->duration * matroska->time_scale >= prebuffered_ns) ? -1 : 0;
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}
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// The prebuffer ends in the last Cue. Estimate how much data was
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// prebuffered.
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pre_bytes = desc_end.end_offset - desc_end.start_offset;
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pre_ns = desc_end.end_time_ns - desc_end.start_time_ns;
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pre_sec = pre_ns / nano_seconds_per_second;
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prebuffer_bytes +=
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pre_bytes * ((temp_prebuffer_ns / nano_seconds_per_second) / pre_sec);
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prebuffer = prebuffer_ns / nano_seconds_per_second;
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// Set this to 0.0 in case our prebuffer buffers the entire video.
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bits_per_second = 0.0;
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do {
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int64_t desc_bytes = desc_end.end_offset - desc_beg.start_offset;
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int64_t desc_ns = desc_end.end_time_ns - desc_beg.start_time_ns;
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double desc_sec = desc_ns / nano_seconds_per_second;
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double calc_bits_per_second = (desc_bytes * 8) / desc_sec;
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// Drop the bps by the percentage of bytes buffered.
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double percent = (desc_bytes - prebuffer_bytes) / desc_bytes;
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double mod_bits_per_second = calc_bits_per_second * percent;
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if (prebuffer < desc_sec) {
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double search_sec =
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(double)(matroska->duration * matroska->time_scale) / nano_seconds_per_second;
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// Add 1 so the bits per second should be a little bit greater than file
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// datarate.
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int64_t bps = (int64_t)(mod_bits_per_second) + 1;
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const double min_buffer = 0.0;
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double buffer = prebuffer;
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double sec_to_download = 0.0;
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int rv = buffer_size_after_time_downloaded(prebuffered_ns, search_sec, bps,
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min_buffer, &buffer, &sec_to_download,
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s, cues_start);
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if (rv < 0) {
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return -1;
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} else if (rv == 0) {
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bits_per_second = (double)(bps);
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break;
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}
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}
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desc_end = get_cue_desc(s, desc_end.end_time_ns, cues_start);
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} while (desc_end.start_time_ns != -1);
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if (bandwidth < bits_per_second) bandwidth = bits_per_second;
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}
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return (int64_t)bandwidth;
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}
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static int webm_dash_manifest_cues(AVFormatContext *s)
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{
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MatroskaDemuxContext *matroska = s->priv_data;
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EbmlList *seekhead_list = &matroska->seekhead;
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MatroskaSeekhead *seekhead = seekhead_list->elem;
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char *buf;
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int64_t cues_start, cues_end, before_pos, bandwidth;
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int i;
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// determine cues start and end positions
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for (i = 0; i < seekhead_list->nb_elem; i++)
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if (seekhead[i].id == MATROSKA_ID_CUES)
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break;
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if (i >= seekhead_list->nb_elem) return -1;
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before_pos = avio_tell(matroska->ctx->pb);
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cues_start = seekhead[i].pos + matroska->segment_start;
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if (avio_seek(matroska->ctx->pb, cues_start, SEEK_SET) == cues_start) {
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uint64_t cues_length = 0, cues_id = 0;
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ebml_read_num(matroska, matroska->ctx->pb, 4, &cues_id);
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ebml_read_length(matroska, matroska->ctx->pb, &cues_length);
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cues_end = cues_start + cues_length + 11; // 11 is the offset of Cues ID.
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}
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avio_seek(matroska->ctx->pb, before_pos, SEEK_SET);
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// parse the cues
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matroska_parse_cues(matroska);
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// cues start
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buf = av_asprintf("%" PRId64, cues_start);
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if (!buf) return AVERROR(ENOMEM);
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av_dict_set(&s->streams[0]->metadata, CUES_START, buf, 0);
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av_free(buf);
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// cues end
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buf = av_asprintf("%" PRId64, cues_end);
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if (!buf) return AVERROR(ENOMEM);
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av_dict_set(&s->streams[0]->metadata, CUES_END, buf, 0);
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av_free(buf);
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// bandwidth
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bandwidth = webm_dash_manifest_compute_bandwidth(s, cues_start);
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if (bandwidth < 0) return -1;
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buf = av_asprintf("%" PRId64, bandwidth);
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if (!buf) return AVERROR(ENOMEM);
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av_dict_set(&s->streams[0]->metadata, BANDWIDTH, buf, 0);
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av_free(buf);
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// check if all clusters start with key frames
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buf = av_asprintf("%d", webm_clusters_start_with_keyframe(s));
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if (!buf) return AVERROR(ENOMEM);
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av_dict_set(&s->streams[0]->metadata, CLUSTER_KEYFRAME, buf, 0);
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av_free(buf);
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// store cue point timestamps as a comma separated list for checking subsegment alignment in
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// the muxer. assumes that each timestamp cannot be more than 20 characters long.
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buf = av_malloc(s->streams[0]->nb_index_entries * 20 * sizeof(char));
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if (!buf) return -1;
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strcpy(buf, "");
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for (i = 0; i < s->streams[0]->nb_index_entries; i++) {
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snprintf(buf, (i + 1) * 20 * sizeof(char),
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"%s%" PRId64, buf, s->streams[0]->index_entries[i].timestamp);
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if (i != s->streams[0]->nb_index_entries - 1)
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strncat(buf, ",", sizeof(char));
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}
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av_dict_set(&s->streams[0]->metadata, CUE_TIMESTAMPS, buf, 0);
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av_free(buf);
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return 0;
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}
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static int webm_dash_manifest_read_header(AVFormatContext *s)
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{
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char *buf;
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int ret = matroska_read_header(s);
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MatroskaTrack *tracks;
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MatroskaDemuxContext *matroska = s->priv_data;
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if (ret) {
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av_log(s, AV_LOG_ERROR, "Failed to read file headers\n");
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return -1;
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}
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// initialization range
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buf = av_asprintf("%" PRId64, avio_tell(s->pb) - 5); // 5 is the offset of Cluster ID.
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if (!buf) return AVERROR(ENOMEM);
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av_dict_set(&s->streams[0]->metadata, INITIALIZATION_RANGE, buf, 0);
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av_free(buf);
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// basename of the file
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buf = strrchr(s->filename, '/');
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if (buf == NULL) return -1;
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av_dict_set(&s->streams[0]->metadata, FILENAME, ++buf, 0);
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// duration
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buf = av_asprintf("%g", matroska->duration);
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if (!buf) return AVERROR(ENOMEM);
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av_dict_set(&s->streams[0]->metadata, DURATION, buf, 0);
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av_free(buf);
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// track number
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tracks = matroska->tracks.elem;
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buf = av_asprintf("%" PRId64, tracks[0].num);
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if (!buf) return AVERROR(ENOMEM);
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av_dict_set(&s->streams[0]->metadata, TRACK_NUMBER, buf, 0);
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av_free(buf);
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// parse the cues and populate Cue related fields
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return webm_dash_manifest_cues(s);
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}
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static int webm_dash_manifest_read_packet(AVFormatContext *s, AVPacket *pkt)
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{
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return AVERROR_EOF;
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}
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AVInputFormat ff_matroska_demuxer = {
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.name = "matroska,webm",
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.long_name = NULL_IF_CONFIG_SMALL("Matroska / WebM"),
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@ -3078,3 +3437,12 @@ AVInputFormat ff_matroska_demuxer = {
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.read_close = matroska_read_close,
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.read_seek = matroska_read_seek,
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};
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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,
|
||||
};
|
||||
|
||||
Loading…
Reference in New Issue
Block a user