[FFmpeg-devel,v2,2/2] avformat/hls: Add subtitle support

Submitted by Franklin Phillips on Feb. 5, 2017, 7:43 p.m.

Details

Message ID 20170205194344.333-2-franklinphillips@gmx.com
State New
Headers show

Commit Message

Franklin Phillips Feb. 5, 2017, 7:43 p.m.
Each subtile segment is a WebVTT file and needs to be demuxed
separately. These segments also contain a header to synchronize their
timing with the MPEG TS stream so those timestamps are requested from
the WebVTT demuxer through an AVOption.

Signed-off-by: Franklin Phillips <franklinphillips@gmx.com>
---
 libavformat/hls.c | 195 ++++++++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 161 insertions(+), 34 deletions(-)

Patch hide | download patch | download mbox

diff --git a/libavformat/hls.c b/libavformat/hls.c
index 3ae3c7c..fe6fec4 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 it's a subtitle playlist */
 };
 
 /*
@@ -203,6 +205,7 @@  typedef struct HLSContext {
     char *headers;                       ///< holds HTTP headers set as an AVOption to the HTTP protocol context
     char *http_proxy;                    ///< holds the address of the HTTP proxy server
     AVDictionary *avio_opts;
+    AVDictionary *demuxer_opts;
     int strict_std_compliance;
 } HLSContext;
 
@@ -309,6 +312,8 @@  static struct playlist *new_playlist(HLSContext *c, const char *url,
     ff_make_absolute_url(pls->url, sizeof(pls->url), base, url);
     pls->seek_timestamp = AV_NOPTS_VALUE;
 
+    pls->is_subtitle = 0;
+
     pls->is_id3_timestamped = -1;
     pls->id3_mpegts_timestamp = AV_NOPTS_VALUE;
 
@@ -482,11 +487,6 @@  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 +501,14 @@  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]) {
@@ -1237,24 +1242,20 @@  static int64_t default_reload_interval(struct playlist *pls)
                           pls->target_duration;
 }
 
-static int read_data(void *opaque, uint8_t *buf, int buf_size)
+static int reload_playlist(struct playlist *v, HLSContext *c)
 {
-    struct playlist *v = opaque;
-    HLSContext *c = v->parent->priv_data;
-    int ret, i;
-    int just_opened = 0;
+    int ret = 0;
 
-restart:
     if (!v->needed)
         return AVERROR_EOF;
 
     if (!v->input) {
         int64_t reload_interval;
-        struct segment *seg;
 
         /* Check that the playlist is still needed before opening a new
          * segment. */
-        if (v->ctx && v->ctx->nb_streams) {
+        if ((v->ctx && v->ctx->nb_streams) || v->is_subtitle) {
+            int i;
             v->needed = 0;
             for (i = 0; i < v->n_main_streams; i++) {
                 if (v->main_streams[i]->discard < AVDISCARD_ALL) {
@@ -1293,7 +1294,7 @@  reload:
             v->cur_seq_no = v->start_seq_no;
         }
         if (v->cur_seq_no >= v->start_seq_no + v->n_segments) {
-            if (v->finished)
+            if (v->finished || v->is_subtitle)
                 return AVERROR_EOF;
             while (av_gettime_relative() - v->last_load_time < reload_interval) {
                 if (ff_check_interrupt(c->interrupt_callback))
@@ -1303,12 +1304,28 @@  reload:
             /* Enough time has elapsed since the last reload */
             goto reload;
         }
+    }
 
-        seg = current_segment(v);
+    return ret;
+}
 
+static int read_data_continuous(void *opaque, uint8_t *buf, int buf_size)
+{
+    struct playlist *v = opaque;
+    HLSContext *c = v->parent->priv_data;
+    int ret, just_opened = 0;
+    struct segment *seg;
+
+restart:
+    ret = reload_playlist(v, c);
+    if (ret < 0)
+        return ret;
+    seg = current_segment(v);
+
+    if (!v->input) {
         /* load/update Media Initialization Section, if any */
         ret = update_init_section(v, seg);
-        if (ret)
+        if (ret < 0)
             return ret;
 
         ret = open_input(c, v, seg);
@@ -1318,7 +1335,7 @@  reload:
             av_log(v->parent, AV_LOG_WARNING, "Failed to open segment of playlist %d\n",
                    v->index);
             v->cur_seq_no += 1;
-            goto reload;
+            goto restart;
         }
         just_opened = 1;
     }
@@ -1331,7 +1348,7 @@  reload:
         return copy_size;
     }
 
-    ret = read_from_url(v, current_segment(v), buf, buf_size, READ_NORMAL);
+    ret = read_from_url(v, seg, 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
@@ -1343,9 +1360,109 @@  reload:
     }
     ff_format_io_close(v->parent, &v->input);
     v->cur_seq_no++;
+    c->cur_seq_no = v->cur_seq_no;
+
+    goto restart;
+}
+
+static int read_data_subtitle_segment(void *opaque, uint8_t *buf, int buf_size)
+{
+    struct playlist *v = opaque;
+    HLSContext *c = v->parent->priv_data;
+    int ret;
+    struct segment *seg;
 
+    if (!v->needed || v->cur_seq_no - v->start_seq_no >= v->n_segments) {
+        return AVERROR_EOF;
+    } else {
+        seg = current_segment(v);
+    }
+
+    if (!v->input) {
+        ret = open_input(c, v, seg);
+        if (ret < 0) {
+            if (ff_check_interrupt(c->interrupt_callback))
+                return AVERROR_EXIT;
+            av_log(v->parent, AV_LOG_WARNING, "Failed to open segment of playlist %d\n",
+                   v->index);
+            return ret;
+        }
+    }
+
+    return read_from_url(v, seg, buf, buf_size, READ_NORMAL);
+}
+
+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 init_subtitle_context(struct playlist *pls)
+{
+    HLSContext *c = pls->parent->priv_data;
+    AVInputFormat *in_fmt;
+    AVDictionary *opts = NULL;
+    int ret = 0;
+
+    if (!(pls->ctx = avformat_alloc_context()))
+        return AVERROR(ENOMEM);
+
+    pls->read_buffer = av_malloc(INITIAL_BUFFER_SIZE);
+    if (!pls->read_buffer) {
+        avformat_free_context(pls->ctx);
+        pls->ctx = NULL;
+        return AVERROR(ENOMEM);
+    }
+
+    ffio_init_context(&pls->pb, pls->read_buffer, INITIAL_BUFFER_SIZE, 0, pls,
+                      read_data_subtitle_segment, NULL, NULL);
+    pls->pb.seekable = 0;
+    pls->ctx->pb = &pls->pb;
+    pls->ctx->io_open = nested_io_open;
+
+    ret = ff_copy_whiteblacklists(pls->ctx, pls->parent);
+    if (ret < 0)
+        return ret;
+
+    in_fmt = av_find_input_format("webvtt");
+    av_dict_copy(&opts, c->demuxer_opts, 0);
+    ret = avformat_open_input(&pls->ctx, current_segment(pls)->url, in_fmt, &opts);
+    av_dict_free(&opts);
+
+    return ret;
+}
+
+static int read_subtitle_packet(struct playlist *v, AVPacket *pkt)
+{
+    HLSContext *c = v->parent->priv_data;
+    int ret;
+
+restart:
+    ret = reload_playlist(v, c);
+    if (ret < 0)
+        return ret;
+
+    if (!v->input && !v->ctx) {
+        ret = init_subtitle_context(v);
+        if (ret < 0)
+            return ret;
+    }
+
+    ret = av_read_frame(v->ctx, &v->pkt);
+    if (!ret) {
+        return ret;
+    }
+    ff_format_io_close(v->parent, &v->input);
+    v->cur_seq_no++;
     c->cur_seq_no = v->cur_seq_no;
 
+    avformat_close_input(&v->ctx);
+
     goto restart;
 }
 
@@ -1492,16 +1609,6 @@  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;
@@ -1602,6 +1709,7 @@  static int hls_close(AVFormatContext *s)
     free_rendition_list(c);
 
     av_dict_free(&c->avio_opts);
+    av_dict_free(&c->demuxer_opts);
 
     return 0;
 }
@@ -1708,10 +1816,13 @@  static int hls_read_header(AVFormatContext *s)
         highest_cur_seq_no = FFMAX(highest_cur_seq_no, pls->cur_seq_no);
     }
 
+    av_dict_set(&c->demuxer_opts, "prefer_hls_mpegts_pts", "1", 0);
+
     /* Open the demuxer for each playlist */
     for (i = 0; i < c->n_playlists; i++) {
         struct playlist *pls = c->playlists[i];
         AVInputFormat *in_fmt = NULL;
+        AVDictionary *opts = NULL;
 
         if (!(pls->ctx = avformat_alloc_context())) {
             ret = AVERROR(ENOMEM);
@@ -1744,9 +1855,14 @@  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_subtitle_segment, NULL, NULL);
+        else
+            ffio_init_context(&pls->pb, pls->read_buffer, INITIAL_BUFFER_SIZE, 0, pls,
+                                      read_data_continuous, NULL, NULL);
         pls->pb.seekable = 0;
+
         ret = av_probe_input_buffer(&pls->pb, &in_fmt, pls->segments[0]->url,
                                     NULL, 0, 0);
         if (ret < 0) {
@@ -1765,7 +1881,9 @@  static int hls_read_header(AVFormatContext *s)
         if ((ret = ff_copy_whiteblacklists(pls->ctx, s)) < 0)
             goto fail;
 
-        ret = avformat_open_input(&pls->ctx, pls->segments[0]->url, in_fmt, NULL);
+        av_dict_copy(&opts, c->demuxer_opts, 0);
+        ret = avformat_open_input(&pls->ctx, pls->segments[0]->url, in_fmt, &opts);
+        av_dict_free(&opts);
         if (ret < 0)
             goto fail;
 
@@ -1843,6 +1961,8 @@  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 +2029,10 @@  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_subtitle_packet(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;
@@ -2085,7 +2208,11 @@  static int hls_read_seek(AVFormatContext *s, int stream_index,
         /* Reset the pos, to let the mpegts demuxer know we've seeked. */
         pls->pb.pos = 0;
         /* Flush the packet queue of the subdemuxer. */
-        ff_read_frame_flush(pls->ctx);
+        if (pls->ctx)
+            ff_read_frame_flush(pls->ctx);
+
+        if (pls->is_subtitle)
+            avformat_close_input(&pls->ctx);
 
         pls->seek_timestamp = seek_timestamp;
         pls->seek_flags = flags;