[FFmpeg-devel] [PATCH 8/9] fftools/ffmpeg: use a separate variable for discontinuity offset

[Anton Khirnov]

This will allow to move normal offset handling to demuxer thread, since
discontinuities currently have to be processed in the main thread, as
the code uses some decoder-produced values.
---
 fftools/ffmpeg.c | 39 ++++++++++++++++++++++++++++-----------
 fftools/ffmpeg.h |  4 ++++
 2 files changed, 32 insertions(+), 11 deletions(-)

diff --git a/fftools/ffmpeg.c b/fftools/ffmpeg.c
index dd45cb4516..8d85af1c97 100644
--- a/fftools/ffmpeg.c
+++ b/fftools/ffmpeg.c
@@ -3693,8 +3693,8 @@ static void decode_flush(InputFile *ifile)
     }
 }
 
-static void ts_discontinuity_process(InputFile *ifile, InputStream *ist,
-                                     AVPacket *pkt)
+static void ts_discontinuity_detect(InputFile *ifile, InputStream *ist,
+                                    AVPacket *pkt)
 {
     const int fmt_is_discont = ifile->ctx->iformat->flags & AVFMT_TS_DISCONT;
     int disable_discontinuity_correction = copy_ts;
@@ -3715,13 +3715,13 @@ static void ts_discontinuity_process(InputFile *ifile, InputStream *ist,
         if (fmt_is_discont) {
             if (FFABS(delta) > 1LL * dts_delta_threshold * AV_TIME_BASE ||
                 pkt_dts + AV_TIME_BASE/10 < FFMAX(ist->pts, ist->dts)) {
-                ifile->ts_offset -= delta;
+                ifile->ts_offset_discont -= delta;
                 av_log(NULL, AV_LOG_DEBUG,
                        "timestamp discontinuity for stream #%d:%d "
                        "(id=%d, type=%s): %"PRId64", new offset= %"PRId64"\n",
                        ist->file_index, ist->st->index, ist->st->id,
                        av_get_media_type_string(ist->st->codecpar->codec_type),
-                       delta, ifile->ts_offset);
+                       delta, ifile->ts_offset_discont);
                 pkt->dts -= av_rescale_q(delta, AV_TIME_BASE_Q, ist->st->time_base);
                 if (pkt->pts != AV_NOPTS_VALUE)
                     pkt->pts -= av_rescale_q(delta, AV_TIME_BASE_Q, ist->st->time_base);
@@ -3744,10 +3744,10 @@ static void ts_discontinuity_process(InputFile *ifile, InputStream *ist,
                fmt_is_discont && ifile->last_ts != AV_NOPTS_VALUE) {
         int64_t delta = pkt_dts - ifile->last_ts;
         if (FFABS(delta) > 1LL * dts_delta_threshold * AV_TIME_BASE) {
-            ifile->ts_offset -= delta;
+            ifile->ts_offset_discont -= delta;
             av_log(NULL, AV_LOG_DEBUG,
                    "Inter stream timestamp discontinuity %"PRId64", new offset= %"PRId64"\n",
-                   delta, ifile->ts_offset);
+                   delta, ifile->ts_offset_discont);
             pkt->dts -= av_rescale_q(delta, AV_TIME_BASE_Q, ist->st->time_base);
             if (pkt->pts != AV_NOPTS_VALUE)
                 pkt->pts -= av_rescale_q(delta, AV_TIME_BASE_Q, ist->st->time_base);
@@ -3757,6 +3757,26 @@ static void ts_discontinuity_process(InputFile *ifile, InputStream *ist,
     ifile->last_ts = av_rescale_q(pkt->dts, ist->st->time_base, AV_TIME_BASE_Q);
 }
 
+static void ts_discontinuity_process(InputFile *ifile, InputStream *ist,
+                                     AVPacket *pkt)
+{
+    int64_t offset = av_rescale_q(ifile->ts_offset_discont, AV_TIME_BASE_Q,
+                                  ist->st->time_base);
+
+    // apply previously-detected timestamp-discontinuity offset
+    // (to all streams, not just audio/video)
+    if (pkt->dts != AV_NOPTS_VALUE)
+        pkt->dts += offset;
+    if (pkt->pts != AV_NOPTS_VALUE)
+        pkt->pts += offset;
+
+    // detect timestamp discontinuities for audio/video
+    if ((ist->st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO ||
+         ist->st->codecpar->codec_type == AVMEDIA_TYPE_AUDIO) &&
+        pkt->dts != AV_NOPTS_VALUE)
+        ts_discontinuity_detect(ifile, ist, pkt);
+}
+
 /*
  * Return
  * - 0 -- one packet was read and processed
@@ -3897,11 +3917,8 @@ static int process_input(int file_index)
     if (pkt->dts != AV_NOPTS_VALUE)
         pkt->dts += duration;
 
-    // detect and correct timestamp discontinuities for audio/video
-    if ((ist->st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO ||
-         ist->st->codecpar->codec_type == AVMEDIA_TYPE_AUDIO) &&
-        pkt->dts != AV_NOPTS_VALUE)
-        ts_discontinuity_process(ifile, ist, pkt);
+    // detect and try to correct for timestamp discontinuities
+    ts_discontinuity_process(ifile, ist, pkt);
 
     if (debug_ts) {
         av_log(NULL, AV_LOG_INFO, "demuxer+ffmpeg -> ist_index:%d type:%s pkt_pts:%s pkt_pts_time:%s pkt_dts:%s pkt_dts_time:%s duration:%s duration_time:%s off:%s off_time:%s\n",
diff --git a/fftools/ffmpeg.h b/fftools/ffmpeg.h
index 8b2e73d642..6991ba7632 100644
--- a/fftools/ffmpeg.h
+++ b/fftools/ffmpeg.h
@@ -427,6 +427,10 @@ typedef struct InputFile {
     int input_sync_ref;
 
     int64_t ts_offset;
+    /**
+     * Extra timestamp offset added by discontinuity handling.
+     */
+    int64_t ts_offset_discont;
     int64_t last_ts;
     int64_t start_time;   /* user-specified start time in AV_TIME_BASE or AV_NOPTS_VALUE */
     int64_t recording_time;
-- 
2.34.1