[FFmpeg-devel] [PATCH] avformat/hls: Added subtitle support
wm4
nfxjfg at googlemail.com
Wed Nov 16 12:41:41 EET 2016
On Wed, 16 Nov 2016 10:31:10 +0000
Franklin Phillips <franklinphillips at gmx.com> wrote:
> 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
What does this mean?
> 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).
I'm not entirely familiar how HLS works. Shouldn't this be fine as long
as the webvtt events have the correct "final" timestamp?
>
> Signed-off-by: Franklin Phillips <franklinphillips at gmx.com>
> ---
> 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;
> +}
> +
That seems to duplicate a lot of code from the normal read path...
> 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;
>
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