[FFmpeg-cvslog] avformat/hls: parse ID3 timestamps for elementary audio streams
Anssi Hannula
git at videolan.org
Sun Apr 6 16:56:41 CEST 2014
ffmpeg | branch: master | Anssi Hannula <anssi.hannula at iki.fi> | Sat Apr 5 14:47:26 2014 +0300| [01b184e68d86d6ecd8e7a54b977734d710a917ab] | committer: Anssi Hannula
avformat/hls: parse ID3 timestamps for elementary audio streams
HLS provides MPEG TS timestamps via ID3 tags in the beginning of each
segment of elementary audio streams.
v2: fix issues with streams that have multiple ID3 tags
Signed-off-by: Anssi Hannula <anssi.hannula at iki.fi>
> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=01b184e68d86d6ecd8e7a54b977734d710a917ab
---
libavformat/hls.c | 316 +++++++++++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 305 insertions(+), 11 deletions(-)
diff --git a/libavformat/hls.c b/libavformat/hls.c
index fe14255..dd683e4 100644
--- a/libavformat/hls.c
+++ b/libavformat/hls.c
@@ -27,6 +27,7 @@
*/
#include "libavutil/avstring.h"
+#include "libavutil/avassert.h"
#include "libavutil/intreadwrite.h"
#include "libavutil/mathematics.h"
#include "libavutil/opt.h"
@@ -36,12 +37,16 @@
#include "internal.h"
#include "avio_internal.h"
#include "url.h"
+#include "id3v2.h"
#define INITIAL_BUFFER_SIZE 32768
#define MAX_FIELD_LEN 64
#define MAX_CHARACTERISTICS_LEN 512
+#define MPEG_TIME_BASE 90000
+#define MPEG_TIME_BASE_Q (AVRational){1, MPEG_TIME_BASE}
+
/*
* An apple http stream consists of a playlist with media segment files,
* played sequentially. There may be several playlists with the same
@@ -100,6 +105,18 @@ struct playlist {
char key_url[MAX_URL_SIZE];
uint8_t key[16];
+ /* ID3 timestamp handling (elementary audio streams have ID3 timestamps
+ * (and possibly other ID3 tags) in the beginning of each segment) */
+ int is_id3_timestamped; /* -1: not yet known */
+ int64_t id3_mpegts_timestamp; /* in mpegts tb */
+ int64_t id3_offset; /* in stream original tb */
+ uint8_t* id3_buf; /* temp buffer for id3 parsing */
+ unsigned int id3_buf_size;
+ AVDictionary *id3_initial; /* data from first id3 tag */
+ int id3_found; /* ID3 tag found at some point */
+ int id3_changed; /* ID3 tag data has changed at some point */
+ ID3v2ExtraMeta *id3_deferred_extra; /* stored here until subdemuxer is opened */
+
/* Renditions associated with this playlist, if any.
* Alternative rendition playlists have a single rendition associated
* with them, and variant main Media Playlists may have
@@ -179,6 +196,9 @@ static void free_playlist_list(HLSContext *c)
struct playlist *pls = c->playlists[i];
free_segment_list(pls);
av_freep(&pls->renditions);
+ av_freep(&pls->id3_buf);
+ av_dict_free(&pls->id3_initial);
+ ff_id3v2_free_extra_meta(&pls->id3_deferred_extra);
av_free_packet(&pls->pkt);
av_free(pls->pb.buffer);
if (pls->input)
@@ -234,6 +254,10 @@ static struct playlist *new_playlist(HLSContext *c, const char *url,
return NULL;
reset_packet(&pls->pkt);
ff_make_absolute_url(pls->url, sizeof(pls->url), base, url);
+
+ pls->is_id3_timestamped = -1;
+ pls->id3_mpegts_timestamp = AV_NOPTS_VALUE;
+
dynarray_add(&c->playlists, &c->n_playlists, pls);
return pls;
}
@@ -600,8 +624,14 @@ fail:
return ret;
}
+enum ReadFromURLMode {
+ READ_NORMAL,
+ READ_COMPLETE,
+};
+
/* read from URLContext, limiting read to current segment */
-static int read_from_url(struct playlist *pls, uint8_t *buf, int buf_size)
+static int read_from_url(struct playlist *pls, uint8_t *buf, int buf_size,
+ enum ReadFromURLMode mode)
{
int ret;
struct segment *seg = pls->segments[pls->cur_seq_no - pls->start_seq_no];
@@ -610,7 +640,10 @@ static int read_from_url(struct playlist *pls, uint8_t *buf, int buf_size)
if (seg->size >= 0)
buf_size = FFMIN(buf_size, seg->size - pls->cur_seg_offset);
- ret = ffurl_read(pls->input, buf, buf_size);
+ if (mode == READ_COMPLETE)
+ ret = ffurl_read_complete(pls->input, buf, buf_size);
+ else
+ ret = ffurl_read(pls->input, buf, buf_size);
if (ret > 0)
pls->cur_seg_offset += ret;
@@ -618,6 +651,204 @@ static int read_from_url(struct playlist *pls, uint8_t *buf, int buf_size)
return ret;
}
+/* Parse the raw ID3 data and pass contents to caller */
+static void parse_id3(AVFormatContext *s, AVIOContext *pb,
+ AVDictionary **metadata, int64_t *dts,
+ ID3v2ExtraMetaAPIC **apic, ID3v2ExtraMeta **extra_meta)
+{
+ static const char id3_priv_owner_ts[] = "com.apple.streaming.transportStreamTimestamp";
+ ID3v2ExtraMeta *meta;
+
+ ff_id3v2_read_dict(pb, metadata, ID3v2_DEFAULT_MAGIC, extra_meta);
+ for (meta = *extra_meta; meta; meta = meta->next) {
+ if (!strcmp(meta->tag, "PRIV")) {
+ ID3v2ExtraMetaPRIV *priv = meta->data;
+ if (priv->datasize == 8 && !strcmp(priv->owner, id3_priv_owner_ts)) {
+ /* 33-bit MPEG timestamp */
+ int64_t ts = AV_RB64(priv->data);
+ av_log(s, AV_LOG_DEBUG, "HLS ID3 audio timestamp %"PRId64"\n", ts);
+ if ((ts & ~((1ULL << 33) - 1)) == 0)
+ *dts = ts;
+ else
+ av_log(s, AV_LOG_ERROR, "Invalid HLS ID3 audio timestamp %"PRId64"\n", ts);
+ }
+ } else if (!strcmp(meta->tag, "APIC") && apic)
+ *apic = meta->data;
+ }
+}
+
+/* Check if the ID3 metadata contents have changed */
+static int id3_has_changed_values(struct playlist *pls, AVDictionary *metadata,
+ ID3v2ExtraMetaAPIC *apic)
+{
+ AVDictionaryEntry *entry = NULL;
+ AVDictionaryEntry *oldentry;
+ /* check that no keys have changed values */
+ while ((entry = av_dict_get(metadata, "", entry, AV_DICT_IGNORE_SUFFIX))) {
+ oldentry = av_dict_get(pls->id3_initial, entry->key, NULL, AV_DICT_MATCH_CASE);
+ if (!oldentry || strcmp(oldentry->value, entry->value) != 0)
+ return 1;
+ }
+
+ /* check if apic appeared */
+ if (apic && (pls->ctx->nb_streams != 2 || !pls->ctx->streams[1]->attached_pic.data))
+ return 1;
+
+ if (apic) {
+ int size = pls->ctx->streams[1]->attached_pic.size;
+ if (size != apic->buf->size - FF_INPUT_BUFFER_PADDING_SIZE)
+ return 1;
+
+ if (memcmp(apic->buf->data, pls->ctx->streams[1]->attached_pic.data, size) != 0)
+ return 1;
+ }
+
+ return 0;
+}
+
+/* Parse ID3 data and handle the found data */
+static void handle_id3(AVIOContext *pb, struct playlist *pls)
+{
+ AVDictionary *metadata = NULL;
+ ID3v2ExtraMetaAPIC *apic = NULL;
+ ID3v2ExtraMeta *extra_meta = NULL;
+ int64_t timestamp = AV_NOPTS_VALUE;
+
+ parse_id3(pls->ctx, pb, &metadata, ×tamp, &apic, &extra_meta);
+
+ if (timestamp != AV_NOPTS_VALUE) {
+ pls->id3_mpegts_timestamp = timestamp;
+ pls->id3_offset = 0;
+ }
+
+ if (!pls->id3_found) {
+ /* initial ID3 tags */
+ av_assert0(!pls->id3_deferred_extra);
+ pls->id3_found = 1;
+
+ /* get picture attachment and set text metadata */
+ if (pls->ctx->nb_streams)
+ ff_id3v2_parse_apic(pls->ctx, &extra_meta);
+ else
+ /* demuxer not yet opened, defer picture attachment */
+ pls->id3_deferred_extra = extra_meta;
+
+ av_dict_copy(&pls->ctx->metadata, metadata, 0);
+ pls->id3_initial = metadata;
+
+ } else {
+ if (!pls->id3_changed && id3_has_changed_values(pls, metadata, apic)) {
+ avpriv_report_missing_feature(pls->ctx, "Changing ID3 metadata in HLS audio elementary stream");
+ pls->id3_changed = 1;
+ }
+ av_dict_free(&metadata);
+ }
+
+ if (!pls->id3_deferred_extra)
+ ff_id3v2_free_extra_meta(&extra_meta);
+}
+
+/* Intercept and handle ID3 tags between URLContext and AVIOContext */
+static void intercept_id3(struct playlist *pls, uint8_t *buf,
+ int buf_size, int *len)
+{
+ /* intercept id3 tags, we do not want to pass them to the raw
+ * demuxer on all segment switches */
+ int bytes;
+ int id3_buf_pos = 0;
+ int fill_buf = 0;
+
+ /* gather all the id3 tags */
+ while (1) {
+ /* see if we can retrieve enough data for ID3 header */
+ if (*len < ID3v2_HEADER_SIZE && buf_size >= ID3v2_HEADER_SIZE) {
+ bytes = read_from_url(pls, buf + *len, ID3v2_HEADER_SIZE - *len, READ_COMPLETE);
+ if (bytes > 0) {
+
+ if (bytes == ID3v2_HEADER_SIZE - *len)
+ /* no EOF yet, so fill the caller buffer again after
+ * we have stripped the ID3 tags */
+ fill_buf = 1;
+
+ *len += bytes;
+
+ } else if (*len <= 0) {
+ /* error/EOF */
+ *len = bytes;
+ fill_buf = 0;
+ }
+ }
+
+ if (*len < ID3v2_HEADER_SIZE)
+ break;
+
+ if (ff_id3v2_match(buf, ID3v2_DEFAULT_MAGIC)) {
+ struct segment *seg = pls->segments[pls->cur_seq_no - pls->start_seq_no];
+ int64_t segsize = seg->size >= 0 ? seg->size : ffurl_size(pls->input);
+ int taglen = ff_id3v2_tag_len(buf);
+ int tag_got_bytes = FFMIN(taglen, *len);
+ int remaining = taglen - tag_got_bytes;
+
+ if (taglen > segsize) {
+ av_log(pls->ctx, AV_LOG_ERROR, "Too large HLS ID3 tag (%d vs %"PRId64")\n",
+ taglen, segsize);
+ break;
+ }
+
+ /*
+ * Copy the id3 tag to our temporary id3 buffer.
+ * We could read a small id3 tag directly without memcpy, but
+ * we would still need to copy the large tags, and handling
+ * both of those cases together with the possibility for multiple
+ * tags would make the handling a bit complex.
+ */
+ pls->id3_buf = av_fast_realloc(pls->id3_buf, &pls->id3_buf_size, id3_buf_pos + taglen);
+ if (!pls->id3_buf)
+ break;
+ memcpy(pls->id3_buf + id3_buf_pos, buf, tag_got_bytes);
+ id3_buf_pos += tag_got_bytes;
+
+ /* strip the intercepted bytes */
+ *len -= tag_got_bytes;
+ memmove(buf, buf + tag_got_bytes, *len);
+ av_log(pls->ctx, AV_LOG_DEBUG, "Stripped %d HLS ID3 bytes\n", tag_got_bytes);
+
+ if (remaining > 0) {
+ /* read the rest of the tag in */
+ if (read_from_url(pls, pls->id3_buf + id3_buf_pos, remaining, READ_COMPLETE) != remaining)
+ break;
+ id3_buf_pos += remaining;
+ av_log(pls->ctx, AV_LOG_DEBUG, "Stripped additional %d HLS ID3 bytes\n", remaining);
+ }
+
+ } else {
+ /* no more ID3 tags */
+ break;
+ }
+ }
+
+ /* re-fill buffer for the caller unless EOF */
+ if (*len >= 0 && (fill_buf || *len == 0)) {
+ bytes = read_from_url(pls, buf + *len, buf_size - *len, READ_NORMAL);
+
+ /* ignore error if we already had some data */
+ if (bytes >= 0)
+ *len += bytes;
+ else if (*len == 0)
+ *len = bytes;
+ }
+
+ if (pls->id3_buf) {
+ /* Now parse all the ID3 tags */
+ AVIOContext id3ioctx;
+ ffio_init_context(&id3ioctx, pls->id3_buf, id3_buf_pos, 0, NULL, NULL, NULL, NULL);
+ handle_id3(&id3ioctx, pls);
+ }
+
+ if (pls->is_id3_timestamped == -1)
+ pls->is_id3_timestamped = (pls->id3_mpegts_timestamp != AV_NOPTS_VALUE);
+}
+
static int open_input(HLSContext *c, struct playlist *pls)
{
AVDictionary *opts = NULL;
@@ -720,6 +951,7 @@ static int read_data(void *opaque, uint8_t *buf, int buf_size)
struct playlist *v = opaque;
HLSContext *c = v->parent->priv_data;
int ret, i;
+ int just_opened = 0;
if (!v->needed)
return AVERROR_EOF;
@@ -769,10 +1001,17 @@ reload:
v->index);
return ret;
}
+ just_opened = 1;
}
- ret = read_from_url(v, buf, buf_size);
+ ret = read_from_url(v, buf, buf_size, READ_NORMAL);
if (ret > 0) {
+ if (just_opened && v->is_id3_timestamped != 0) {
+ /* Intercept ID3 tags here, elementary audio streams are required
+ * to convey timestamps using them in the beginning of each segment. */
+ intercept_id3(v, buf, buf_size, &ret);
+ }
+
return ret;
}
ffurl_close(v->input);
@@ -991,11 +1230,21 @@ static int hls_read_header(AVFormatContext *s)
if (ret < 0)
goto fail;
+ if (pls->id3_deferred_extra && pls->ctx->nb_streams == 1) {
+ ff_id3v2_parse_apic(pls->ctx, &pls->id3_deferred_extra);
+ avformat_queue_attached_pictures(pls->ctx);
+ ff_id3v2_free_extra_meta(&pls->id3_deferred_extra);
+ pls->id3_deferred_extra = NULL;
+ }
+
pls->ctx->ctx_flags &= ~AVFMTCTX_NOHEADER;
ret = avformat_find_stream_info(pls->ctx, NULL);
if (ret < 0)
goto fail;
+ if (pls->is_id3_timestamped == -1)
+ av_log(s, AV_LOG_WARNING, "No expected HTTP requests have been made\n");
+
/* Create new AVStreams for each stream in this playlist */
for (j = 0; j < pls->ctx->nb_streams; j++) {
AVStream *st = avformat_new_stream(s, NULL);
@@ -1005,8 +1254,13 @@ static int hls_read_header(AVFormatContext *s)
goto fail;
}
st->id = i;
- avpriv_set_pts_info(st, ist->pts_wrap_bits, ist->time_base.num, ist->time_base.den);
+
avcodec_copy_context(st->codec, pls->ctx->streams[j]->codec);
+
+ if (pls->is_id3_timestamped) /* custom timestamps via id3 */
+ avpriv_set_pts_info(st, 33, 1, MPEG_TIME_BASE);
+ else
+ avpriv_set_pts_info(st, ist->pts_wrap_bits, ist->time_base.num, ist->time_base.den);
}
add_metadata_from_renditions(s, pls, AVMEDIA_TYPE_AUDIO);
@@ -1093,6 +1347,39 @@ static int recheck_discard_flags(AVFormatContext *s, int first)
return changed;
}
+static void fill_timing_for_id3_timestamped_stream(struct playlist *pls)
+{
+ if (pls->id3_offset >= 0) {
+ pls->pkt.dts = pls->id3_mpegts_timestamp +
+ av_rescale_q(pls->id3_offset,
+ pls->ctx->streams[pls->pkt.stream_index]->time_base,
+ MPEG_TIME_BASE_Q);
+ if (pls->pkt.duration)
+ pls->id3_offset += pls->pkt.duration;
+ else
+ pls->id3_offset = -1;
+ } else {
+ /* there have been packets with unknown duration
+ * since the last id3 tag, should not normally happen */
+ pls->pkt.dts = AV_NOPTS_VALUE;
+ }
+
+ if (pls->pkt.duration)
+ pls->pkt.duration = av_rescale_q(pls->pkt.duration,
+ pls->ctx->streams[pls->pkt.stream_index]->time_base,
+ MPEG_TIME_BASE_Q);
+
+ pls->pkt.pts = AV_NOPTS_VALUE;
+}
+
+static AVRational get_timebase(struct playlist *pls)
+{
+ if (pls->is_id3_timestamped)
+ return MPEG_TIME_BASE_Q;
+
+ return pls->ctx->streams[pls->pkt.stream_index]->time_base;
+}
+
static int hls_read_packet(AVFormatContext *s, AVPacket *pkt)
{
HLSContext *c = s->priv_data;
@@ -1112,7 +1399,7 @@ start:
if (pls->needed && !pls->pkt.data) {
while (1) {
int64_t ts_diff;
- AVStream *st;
+ AVRational tb;
ret = av_read_frame(pls->ctx, &pls->pkt);
if (ret < 0) {
if (!url_feof(&pls->pb) && ret != AVERROR_EOF)
@@ -1120,11 +1407,16 @@ start:
reset_packet(&pls->pkt);
break;
} else {
+ /* stream_index check prevents matching picture attachments etc. */
+ if (pls->is_id3_timestamped && pls->pkt.stream_index == 0) {
+ /* audio elementary streams are id3 timestamped */
+ fill_timing_for_id3_timestamped_stream(pls);
+ }
+
if (c->first_timestamp == AV_NOPTS_VALUE &&
pls->pkt.dts != AV_NOPTS_VALUE)
c->first_timestamp = av_rescale_q(pls->pkt.dts,
- pls->ctx->streams[pls->pkt.stream_index]->time_base,
- AV_TIME_BASE_Q);
+ get_timebase(pls), AV_TIME_BASE_Q);
}
if (c->seek_timestamp == AV_NOPTS_VALUE)
@@ -1135,9 +1427,9 @@ start:
break;
}
- st = pls->ctx->streams[pls->pkt.stream_index];
+ tb = get_timebase(pls);
ts_diff = av_rescale_rnd(pls->pkt.dts, AV_TIME_BASE,
- st->time_base.den, AV_ROUND_DOWN) -
+ tb.den, AV_ROUND_DOWN) -
c->seek_timestamp;
if (ts_diff >= 0 && (c->seek_flags & AVSEEK_FLAG_ANY ||
pls->pkt.flags & AV_PKT_FLAG_KEY)) {
@@ -1160,6 +1452,8 @@ start:
int64_t mindts = minpls->pkt.dts;
AVStream *st = pls->ctx->streams[pls->pkt.stream_index];
AVStream *minst = minpls->ctx->streams[minpls->pkt.stream_index];
+ AVRational tb = get_timebase( pls);
+ AVRational mintb = get_timebase(minpls);
if (dts == AV_NOPTS_VALUE) {
minplaylist = i;
@@ -1169,8 +1463,8 @@ start:
if (minst->start_time != AV_NOPTS_VALUE)
mindts -= minst->start_time;
- if (av_compare_ts(dts, st->time_base,
- mindts, minst->time_base) < 0)
+ if (av_compare_ts(dts, tb,
+ mindts, mintb) < 0)
minplaylist = i;
}
}
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