[FFmpeg-devel] [PATCH] avformat/hls: Add subtitle support
Franklin Phillips
franklinphillips9p8 at inbox.lv
Tue Nov 15 21:11:11 EET 2016
This patch is a fix for ticket #2833.
Each subtitle segment is its own WebVTT file and has to demuxed individually. The timing of the subtitles are not perfect but it is the best I could do and it also does not take into account the X-TIMESTAMP-MAP header in the WebVTT files which is needed to conform to the specification (https://tools.ietf.org/html/draft-pantos-http-live-streaming-20#section-3.5).
Signed-off-by: Franklin Phillips <franklinphillips9p8 at inbox.lv>
---
libavformat/hls.c | 178 ++++++++++++++++++++++++++++++++++++++++++++++++------
1 file changed, 159 insertions(+), 19 deletions(-)
diff --git a/libavformat/hls.c b/libavformat/hls.c
index 3ae3c7c..bf13be4 100644
--- a/libavformat/hls.c
+++ b/libavformat/hls.c
@@ -153,6 +153,8 @@ struct playlist {
* playlist, if any. */
int n_init_sections;
struct segment **init_sections;
+
+ int is_subtitle; /* Indicates if the playlist is for subtitles */
};
/*
@@ -312,6 +314,8 @@ static struct playlist *new_playlist(HLSContext *c, const char *url,
pls->is_id3_timestamped = -1;
pls->id3_mpegts_timestamp = AV_NOPTS_VALUE;
+ pls->is_subtitle = 0;
+
dynarray_add(&c->playlists, &c->n_playlists, pls);
return pls;
}
@@ -482,11 +486,6 @@ static struct rendition *new_rendition(HLSContext *c, struct rendition_info *inf
if (type == AVMEDIA_TYPE_SUBTITLE && !info->uri[0])
return NULL;
- /* TODO: handle subtitles (each segment has to parsed separately) */
- if (c->strict_std_compliance > FF_COMPLIANCE_EXPERIMENTAL)
- if (type == AVMEDIA_TYPE_SUBTITLE)
- return NULL;
-
rend = av_mallocz(sizeof(struct rendition));
if (!rend)
return NULL;
@@ -501,9 +500,14 @@ static struct rendition *new_rendition(HLSContext *c, struct rendition_info *inf
/* add the playlist if this is an external rendition */
if (info->uri[0]) {
rend->playlist = new_playlist(c, info->uri, url_base);
- if (rend->playlist)
+ if (rend->playlist) {
dynarray_add(&rend->playlist->renditions,
&rend->playlist->n_renditions, rend);
+ if (type == AVMEDIA_TYPE_SUBTITLE) {
+ rend->playlist->is_subtitle = 1;
+ rend->playlist->is_id3_timestamped = 0;
+ }
+ }
}
if (info->assoc_language[0]) {
@@ -1349,6 +1353,136 @@ reload:
goto restart;
}
+static int nested_io_open(AVFormatContext *s, AVIOContext **pb, const char *url,
+ int flags, AVDictionary **opts)
+{
+ av_log(s, AV_LOG_ERROR,
+ "A HLS playlist item '%s' referred to an external file '%s'. "
+ "Opening this file was forbidden for security reasons\n",
+ s->filename, url);
+ return AVERROR(EPERM);
+}
+
+static int read_data_simple(void *opaque, uint8_t *buf, int buf_size)
+{
+ struct playlist *v = opaque;
+ HLSContext *c = v->parent->priv_data;
+ struct segment *seg;
+
+ if (v->cur_seq_no >= v->start_seq_no + v->n_segments) {
+ return AVERROR_EOF;
+ } else {
+ seg = current_segment(v);
+ }
+
+ if (!v->input) {
+ open_input(c, v, seg);
+ }
+
+ return read_from_url(v, seg, buf, buf_size, READ_NORMAL);
+}
+
+static int read_packet_subtitle(struct playlist *v, AVPacket *pkt)
+{
+ HLSContext *c = v->parent->priv_data;
+ int ret, i;
+
+restart:
+ if (!v->needed)
+ return AVERROR_EOF;
+
+ if (!v->input) {
+ int64_t reload_interval;
+
+ /* Check that the playlist is still needed before opening a new
+ * segment. */
+ if (v->ctx && v->ctx->nb_streams) {
+ v->needed = 0;
+ for (i = 0; i < v->n_main_streams; i++) {
+ if (v->main_streams[i]->discard < AVDISCARD_ALL) {
+ v->needed = 1;
+ break;
+ }
+ }
+ }
+ if (!v->needed) {
+ av_log(v->parent, AV_LOG_INFO, "No longer receiving playlist %d\n",
+ v->index);
+ return AVERROR_EOF;
+ }
+
+ /* If this is a live stream and the reload interval has elapsed since
+ * the last playlist reload, reload the playlists now. */
+ reload_interval = default_reload_interval(v);
+
+ if (!v->finished &&
+ av_gettime_relative() - v->last_load_time >= reload_interval) {
+ if ((ret = parse_playlist(c, v->url, v, NULL)) < 0) {
+ av_log(v->parent, AV_LOG_WARNING, "Failed to reload playlist %d\n",
+ v->index);
+ return ret;
+ }
+ /* If we need to reload the playlist again below (if
+ * there's still no more segments), switch to a reload
+ * interval of half the target duration. */
+ reload_interval = v->target_duration / 2;
+ }
+ if (v->cur_seq_no < v->start_seq_no) {
+ av_log(NULL, AV_LOG_WARNING,
+ "skipping %d segments ahead, expired from subtitle playlists\n",
+ v->start_seq_no - v->cur_seq_no);
+ v->cur_seq_no = v->start_seq_no;
+ }
+ if (v->cur_seq_no >= v->start_seq_no + v->n_segments) {
+ return AVERROR_EOF;
+ }
+ }
+
+ if (v->ctx == NULL) {
+ AVInputFormat *in_fmt;
+
+ if (!(v->ctx = avformat_alloc_context())) {
+ return AVERROR(ENOMEM);
+ }
+
+ v->read_buffer = av_malloc(INITIAL_BUFFER_SIZE);
+ if (!v->read_buffer){
+ avformat_free_context(v->ctx);
+ v->ctx = NULL;
+ return AVERROR(ENOMEM);
+ }
+
+ ffio_init_context(&v->pb, v->read_buffer, INITIAL_BUFFER_SIZE, 0, v,
+ read_data_simple, NULL, NULL);
+ v->pb.seekable = 0;
+ v->ctx->pb = &v->pb;
+ v->ctx->io_open = nested_io_open;
+
+ ret = ff_copy_whiteblacklists(v->ctx, v->parent);
+ if (ret < 0) {
+ return ret;
+ }
+
+ in_fmt = av_find_input_format("webvtt");
+ ret = avformat_open_input(&v->ctx, current_segment(v)->url, in_fmt, NULL);
+ if (ret < 0) {
+ return ret;
+ }
+ }
+
+ ret = av_read_frame(v->ctx, pkt);
+ if (ret < 0) {
+ ff_format_io_close(v->parent, &v->input);
+ avformat_close_input(&v->ctx);
+ if (ret == AVERROR_EOF) {
+ v->cur_seq_no++;
+ goto restart;
+ }
+ }
+
+ return ret;
+}
+
static void add_renditions_to_variant(HLSContext *c, struct variant *var,
enum AVMediaType type, const char *group_id)
{
@@ -1492,16 +1626,6 @@ static int save_avio_options(AVFormatContext *s)
return ret;
}
-static int nested_io_open(AVFormatContext *s, AVIOContext **pb, const char *url,
- int flags, AVDictionary **opts)
-{
- av_log(s, AV_LOG_ERROR,
- "A HLS playlist item '%s' referred to an external file '%s'. "
- "Opening this file was forbidden for security reasons\n",
- s->filename, url);
- return AVERROR(EPERM);
-}
-
static void add_stream_to_programs(AVFormatContext *s, struct playlist *pls, AVStream *stream)
{
HLSContext *c = s->priv_data;
@@ -1744,8 +1868,14 @@ static int hls_read_header(AVFormatContext *s)
pls->ctx = NULL;
goto fail;
}
- ffio_init_context(&pls->pb, pls->read_buffer, INITIAL_BUFFER_SIZE, 0, pls,
- read_data, NULL, NULL);
+
+ if (pls->is_subtitle) {
+ ffio_init_context(&pls->pb, pls->read_buffer, INITIAL_BUFFER_SIZE, 0, pls,
+ read_data_simple, NULL, NULL);
+ } else {
+ ffio_init_context(&pls->pb, pls->read_buffer, INITIAL_BUFFER_SIZE, 0, pls,
+ read_data, NULL, NULL);
+ }
pls->pb.seekable = 0;
ret = av_probe_input_buffer(&pls->pb, &in_fmt, pls->segments[0]->url,
NULL, 0, 0);
@@ -1843,6 +1973,8 @@ static int recheck_discard_flags(AVFormatContext *s, int first)
} else if (first && !pls->cur_needed && pls->needed) {
if (pls->input)
ff_format_io_close(pls->parent, &pls->input);
+ if (pls->is_subtitle)
+ avformat_close_input(&pls->ctx);
pls->needed = 0;
changed = 1;
av_log(s, AV_LOG_INFO, "No longer receiving playlist %d\n", i);
@@ -1909,7 +2041,12 @@ static int hls_read_packet(AVFormatContext *s, AVPacket *pkt)
while (1) {
int64_t ts_diff;
AVRational tb;
- ret = av_read_frame(pls->ctx, &pls->pkt);
+ if (pls->is_subtitle) {
+ ret = read_packet_subtitle(pls, &pls->pkt);
+ } else {
+ ret = av_read_frame(pls->ctx, &pls->pkt);
+ }
+
if (ret < 0) {
if (!avio_feof(&pls->pb) && ret != AVERROR_EOF)
return ret;
@@ -2087,6 +2224,9 @@ static int hls_read_seek(AVFormatContext *s, int stream_index,
/* Flush the packet queue of the subdemuxer. */
ff_read_frame_flush(pls->ctx);
+ if (pls->is_subtitle)
+ avformat_close_input(&pls->ctx);
+
pls->seek_timestamp = seek_timestamp;
pls->seek_flags = flags;
--
2.1.4
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