[FFmpeg-devel,v2] avformat/mpegts: add merge_pmt_versions option

Submitted by Aman Gupta on May 15, 2018, 7:23 p.m.

Details

Message ID 20180515192344.66526-1-ffmpeg@tmm1.net
State New
Headers show

Commit Message

Aman Gupta May 15, 2018, 7:23 p.m.
From: Aman Gupta <aman@tmm1.net>

This new optional flag makes it easier to deal with mpegts
samples where the PMT is updated and elementary streams move
to different PIDs in the middle of playback.

Previously, new AVStreams were created per PID, and it was up
to the user to figure out which streams had migrated to a new PID
(by iterating over the list of AVProgram and making guesses), and
switch seamlessly to the new AVStream during playback.

Transcoding or remuxing these streams with ffmpeg on the CLI was
also quite painful, and the user would need to extract each set of
PIDs into a separate file and then stitch them back together.

With this new option, the mpegts demuxer will automatically detect
PMT changes and feed data from the new PID to the original AVStream
that was created for the orignal PID. For mpegts samples with
stream_identifier_descriptor available, the unique ID is used to merge
PIDs together. If the stream id is not available, the demuxer attempts
to map PIDs based on their order and relation to the PCR pid.

With this change, I am able to playback and transcode/remux these
two samples which previously caused issues:

    https://tmm1.s3.amazonaws.com/pmt-version-change.ts
    https://kuroko.fushizen.eu/videos/pid_switch_sample.ts

I also have another longer sample which contains multiple PMT
changes, some of which change the ES pids and others which do not:

    https://tmm1.s3.amazonaws.com/multiple-pmt-change.ts

Demuxing this sample with the new option shows several new log
messages as the PMT changes are handled:

    [mpegts @ 0x7ffe18801200] detected PMT change (version=3/4, pcr_pid=0xf98/0xf9b)
    [mpegts @ 0x7ffe18801200] re-using existing video stream 0 (pid=0xf98) for new pid=0xf9b
    [mpegts @ 0x7ffe18801200] re-using existing audio stream 1 (pid=0xf99) for new pid=0xf9c
    [mpegts @ 0x7ffe18801200] re-using existing audio stream 2 (pid=0xf9a) for new pid=0xf9d
    [mpegts @ 0x7ffe18801200] detected PMT change (version=4/5, pcr_pid=0xf9b/0xfa9)
    [mpegts @ 0x7ffe18801200] re-using existing video stream 0 (pid=0xf98) for new pid=0xfa9
    [mpegts @ 0x7ffe18801200] re-using existing audio stream 1 (pid=0xf99) for new pid=0xfaa
    [mpegts @ 0x7ffe18801200] re-using existing audio stream 2 (pid=0xf9a) for new pid=0xfab

Signed-off-by: Aman Gupta <aman@tmm1.net>
---
 doc/demuxers.texi                     |   4 ++
 libavformat/mpegts.c                  | 106 ++++++++++++++++++++++++++++++++--
 tests/fate/mpegts.mak                 |   5 ++
 tests/ref/fate/mpegts-probe-pmt-merge |  32 ++++++++++
 4 files changed, 143 insertions(+), 4 deletions(-)
 create mode 100644 tests/ref/fate/mpegts-probe-pmt-merge

Patch hide | download patch | download mbox

diff --git a/doc/demuxers.texi b/doc/demuxers.texi
index e7c2abce57..2f7d7e0f3a 100644
--- a/doc/demuxers.texi
+++ b/doc/demuxers.texi
@@ -552,6 +552,10 @@  Show the detected raw packet size, cannot be set by the user.
 Scan and combine all PMTs. The value is an integer with value from -1
 to 1 (-1 means automatic setting, 1 means enabled, 0 means
 disabled). Default value is -1.
+
+@item merge_pmt_versions
+Re-use existing streams when a PMT's version is updated and elementary
+streams move to different PIDs. Default value is 0.
 @end table
 
 @section mpjpeg
diff --git a/libavformat/mpegts.c b/libavformat/mpegts.c
index 27b1c30a44..f16eae3235 100644
--- a/libavformat/mpegts.c
+++ b/libavformat/mpegts.c
@@ -84,6 +84,8 @@  typedef struct MpegTSSectionFilter {
     unsigned int end_of_section_reached : 1;
     SectionCallback *section_cb;
     void *opaque;
+    int orig_pcr_pid; /* pmt specific */
+    int last_pcr_pid;
 } MpegTSSectionFilter;
 
 struct MpegTSFilter {
@@ -147,6 +149,7 @@  struct MpegTSContext {
     int scan_all_pmts;
 
     int resync_size;
+    int merge_pmt_versions;
 
     /******************************************/
     /* private mpegts data */
@@ -172,6 +175,8 @@  static const AVOption options[] = {
      {.i64 = 0}, 0, 0, AV_OPT_FLAG_DECODING_PARAM | AV_OPT_FLAG_EXPORT | AV_OPT_FLAG_READONLY },
     {"scan_all_pmts", "scan and combine all PMTs", offsetof(MpegTSContext, scan_all_pmts), AV_OPT_TYPE_BOOL,
      {.i64 = -1}, -1, 1, AV_OPT_FLAG_DECODING_PARAM },
+    {"merge_pmt_versions", "re-use streams when PMT's version/pids change", offsetof(MpegTSContext, merge_pmt_versions), AV_OPT_TYPE_BOOL,
+     {.i64 = 0}, 0, 1,  AV_OPT_FLAG_DECODING_PARAM },
     {"skip_changes", "skip changing / adding streams / programs", offsetof(MpegTSContext, skip_changes), AV_OPT_TYPE_BOOL,
      {.i64 = 0}, 0, 1, 0 },
     {"skip_clear", "skip clearing programs", offsetof(MpegTSContext, skip_clear), AV_OPT_TYPE_BOOL,
@@ -1073,7 +1078,8 @@  static int mpegts_push_data(MpegTSFilter *filter,
                         if (ts->skip_changes)
                             goto skip;
 
-                        pes->st = avformat_new_stream(ts->stream, NULL);
+                        if (!pes->st)
+                            pes->st = avformat_new_stream(ts->stream, NULL);
                         if (!pes->st)
                             return AVERROR(ENOMEM);
                         pes->st->id = pes->pid;
@@ -1983,6 +1989,69 @@  int ff_parse_mpeg2_descriptor(AVFormatContext *fc, AVStream *st, int stream_type
     return 0;
 }
 
+static AVStream *find_matching_stream(MpegTSContext *ts, int pid,
+                                      int stream_id,
+                                      int pcr_pid, int orig_pcr_pid)
+{
+    AVFormatContext *s = ts->stream;
+    int i, orig_pid = orig_pcr_pid + (pid - pcr_pid);
+    AVStream *found = NULL;
+
+    for (i = 0; i < s->nb_streams; i++) {
+        AVStream *st = s->streams[i];
+        if (stream_id != -1) {
+            if (st->stream_identifier == stream_id+1) {
+                found = st;
+                break;
+            }
+        } else if (pcr_pid != orig_pcr_pid && st->id == orig_pid) {
+            found = st;
+            break;
+        }
+    }
+
+    if (found) {
+        av_log(ts->stream, AV_LOG_DEBUG, "re-using existing %s stream %d (pid=0x%x) for new pid=0x%x\n",
+               av_get_media_type_string(found->codecpar->codec_type), i, found->id, pid);
+    }
+
+    return found;
+}
+
+static int parse_stream_identifier_desc(const uint8_t *p, const uint8_t *p_end)
+{
+    const uint8_t **pp = &p;
+    const uint8_t *desc_list_end;
+    const uint8_t *desc_end;
+    int desc_list_len;
+    int desc_len, desc_tag;
+
+    desc_list_len = get16(pp, p_end);
+    if (desc_list_len < 0)
+        return -1;
+    desc_list_len &= 0xfff;
+    desc_list_end  = p + desc_list_len;
+    if (desc_list_end > p_end)
+        return -1;
+
+    while (1) {
+        desc_tag = get8(pp, desc_list_end);
+        if (desc_tag < 0)
+            return -1;
+        desc_len = get8(pp, desc_list_end);
+        if (desc_len < 0)
+            return -1;
+        desc_end = *pp + desc_len;
+        if (desc_end > desc_list_end)
+            return -1;
+
+        if (desc_tag == 0x52) {
+            return get8(pp, desc_end);
+        }
+        *pp = desc_end;
+    }
+}
+
 static int is_pes_stream(int stream_type, uint32_t prog_reg_desc)
 {
     return !(stream_type == 0x13 ||
@@ -2000,6 +2069,8 @@  static void pmt_cb(MpegTSFilter *filter, const uint8_t *section, int section_len
     int program_info_length, pcr_pid, pid, stream_type;
     int desc_list_len;
     uint32_t prog_reg_desc = 0; /* registration descriptor */
+    int last_ver = tssf->last_ver;
+    int stream_id = -1;
 
     int mp4_descr_count = 0;
     Mp4Descr mp4_descr[MAX_MP4_DESCR_COUNT] = { { 0 } };
@@ -2032,6 +2103,14 @@  static void pmt_cb(MpegTSFilter *filter, const uint8_t *section, int section_len
     pcr_pid &= 0x1fff;
     add_pid_to_pmt(ts, h->id, pcr_pid);
     set_pcr_pid(ts->stream, h->id, pcr_pid);
+    if (!tssf->orig_pcr_pid)
+        tssf->orig_pcr_pid = pcr_pid;
+
+    if (last_ver != -1 && h->version != last_ver) {
+        av_log(ts->stream, AV_LOG_DEBUG, "detected PMT change (version=%d/%d, pcr_pid=0x%x/0x%x)\n",
+               last_ver, h->version, tssf->last_pcr_pid, pcr_pid);
+    }
+    tssf->last_pcr_pid = pcr_pid;
 
     av_log(ts->stream, AV_LOG_TRACE, "pcr_pid=0x%x\n", pcr_pid);
 
@@ -2083,14 +2162,22 @@  static void pmt_cb(MpegTSFilter *filter, const uint8_t *section, int section_len
         if (pid < 0)
             goto out;
         pid &= 0x1fff;
+        stream_id = parse_stream_identifier_desc(p, p_end);
         if (pid == ts->current_pid)
             goto out;
 
         /* now create stream */
         if (ts->pids[pid] && ts->pids[pid]->type == MPEGTS_PES) {
             pes = ts->pids[pid]->u.pes_filter.opaque;
+            if (ts->merge_pmt_versions && !pes->st) {
+                st = find_matching_stream(ts, pid, stream_id, pcr_pid, tssf->orig_pcr_pid);
+                if (st) {
+                    pes->st = st;
+                    pes->stream_type = stream_type;
+                }
+            }
             if (!pes->st) {
-                pes->st     = avformat_new_stream(pes->stream, NULL);
+                pes->st = avformat_new_stream(pes->stream, NULL);
                 if (!pes->st)
                     goto out;
                 pes->st->id = pes->pid;
@@ -2100,7 +2187,14 @@  static void pmt_cb(MpegTSFilter *filter, const uint8_t *section, int section_len
             if (ts->pids[pid])
                 mpegts_close_filter(ts, ts->pids[pid]); // wrongly added sdt filter probably
             pes = add_pes_stream(ts, pid, pcr_pid);
-            if (pes) {
+            if (ts->merge_pmt_versions && pes && !pes->st) {
+                st = find_matching_stream(ts, pid, stream_id, pcr_pid, tssf->orig_pcr_pid);
+                if (st) {
+                    pes->st = st;
+                    pes->stream_type = stream_type;
+                }
+            }
+            if (pes && !pes->st) {
                 st = avformat_new_stream(pes->stream, NULL);
                 if (!st)
                     goto out;
@@ -2110,7 +2204,11 @@  static void pmt_cb(MpegTSFilter *filter, const uint8_t *section, int section_len
             int idx = ff_find_stream_index(ts->stream, pid);
             if (idx >= 0) {
                 st = ts->stream->streams[idx];
-            } else {
+            }
+            if (ts->merge_pmt_versions && !st) {
+                st = find_matching_stream(ts, pid, stream_id, pcr_pid, tssf->orig_pcr_pid);
+            }
+            if (!st) {
                 st = avformat_new_stream(ts->stream, NULL);
                 if (!st)
                     goto out;
diff --git a/tests/fate/mpegts.mak b/tests/fate/mpegts.mak
index 2b128492e0..bbcbfc47b2 100644
--- a/tests/fate/mpegts.mak
+++ b/tests/fate/mpegts.mak
@@ -15,6 +15,11 @@  fate-mpegts-probe-program: SRC = $(TARGET_SAMPLES)/mpegts/loewe.ts
 fate-mpegts-probe-program: CMD = run $(PROBE_CODEC_NAME_COMMAND) -select_streams p:769:v:0 -i "$(SRC)"
 
 
+FATE_MPEGTS_PROBE-$(call DEMDEC, MPEGTS) += fate-mpegts-probe-pmt-merge
+fate-mpegts-probe-pmt-merge: SRC = $(TARGET_SAMPLES)/mpegts/pmtchange.ts
+fate-mpegts-probe-pmt-merge: CMD = run $(PROBE_CODEC_NAME_COMMAND) -merge_pmt_versions 1 -i "$(SRC)"
+
+
 FATE_SAMPLES_FFPROBE += $(FATE_MPEGTS_PROBE-yes)
 
 fate-mpegts: $(FATE_MPEGTS_PROBE-yes)
diff --git a/tests/ref/fate/mpegts-probe-pmt-merge b/tests/ref/fate/mpegts-probe-pmt-merge
new file mode 100644
index 0000000000..6e424af5d2
--- /dev/null
+++ b/tests/ref/fate/mpegts-probe-pmt-merge
@@ -0,0 +1,32 @@ 
+[PROGRAM]
+[STREAM]
+codec_name=ac3
+[/STREAM]
+[STREAM]
+codec_name=ac3
+[/STREAM]
+[STREAM]
+codec_name=ac3
+[/STREAM]
+[STREAM]
+codec_name=mpeg2video
+[/STREAM]
+[STREAM]
+codec_name=scte_35
+[/STREAM]
+[/PROGRAM]
+[STREAM]
+codec_name=ac3
+[/STREAM]
+[STREAM]
+codec_name=ac3
+[/STREAM]
+[STREAM]
+codec_name=ac3
+[/STREAM]
+[STREAM]
+codec_name=mpeg2video
+[/STREAM]
+[STREAM]
+codec_name=scte_35
+[/STREAM]