On Wed, Nov 16, 2016 at 11:41:41AM +0100, wm4 wrote: > On Wed, 16 Nov 2016 10:31:10 +0000 > Franklin Phillips <[email protected]> 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? > When I convert a mp4 file with subtitles into hls and then back into mp4, the subtitles are off by a couple 100 milliseconds usually. It seems to be caused by the first audio/video packet not having a 0 timestamp causing ffmpeg to subtract the timestamp of that first packet from all the subsequent packets.
> > 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? > Yes, I believe so, the fall back in the specification is to assume the value of that header is 0 meaning no offset and all the examples I've seen have that value set to 0 anyway. I don't think it's a crucial feature that needs to be done ASAP. > > > > Signed-off-by: Franklin Phillips <[email protected]> > > --- > > 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... > I don't think there is a lot of duplication, and the duplication that there is, I don't think can be factored out cleanly due to the different ways the two methods are called and the difference in behaviour of the two methods. > > 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; > > > > _______________________________________________ > ffmpeg-devel mailing list > [email protected] > http://ffmpeg.org/mailman/listinfo/ffmpeg-devel _______________________________________________ ffmpeg-devel mailing list [email protected] http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
