ffmpeg: add option readrate

Allows to read inputs at arbitrary rates.
-re is equivalent to -readrate 1

Tested with -copyts {+ start_at_zero}, -ss, streamcopied & decoded streams.

1 files changed, 10 insertions, 3 deletions

diff --git a/fftools/ffmpeg.c b/fftools/ffmpeg.c
index 1ac2e48600..e0f2fe138f 100644
--- a/fftools/ffmpeg.c
+++ b/fftools/ffmpeg.c
@@ -3765,7 +3765,7 @@ static int transcode_init(void)
     /* init framerate emulation */
     for (i = 0; i < nb_input_files; i++) {
         InputFile *ifile = input_files[i];
-        if (ifile->rate_emu)
+        if (ifile->readrate || ifile->rate_emu)
             for (j = 0; j < ifile->nb_streams; j++)
                 input_streams[j + ifile->ist_index]->start = av_gettime_relative();
     }
@@ -4225,12 +4225,19 @@ static int get_input_packet_mt(InputFile *f, AVPacket **pkt)
 
 static int get_input_packet(InputFile *f, AVPacket **pkt)
 {
-    if (f->rate_emu) {
+    if (f->readrate || f->rate_emu) {
         int i;
+        int64_t file_start = copy_ts * (
+                              (f->ctx->start_time != AV_NOPTS_VALUE ? f->ctx->start_time * !start_at_zero : 0) +
+                              (f->start_time != AV_NOPTS_VALUE ? f->start_time : 0)
+                             );
+        float scale = f->rate_emu ? 1.0 : f->readrate;
         for (i = 0; i < f->nb_streams; i++) {
             InputStream *ist = input_streams[f->ist_index + i];
+            if (!ist->nb_packets) continue;
+            int64_t stream_ts_offset = FFMAX(ist->first_dts != AV_NOPTS_VALUE ? ist->first_dts : 0, file_start);
             int64_t pts = av_rescale(ist->dts, 1000000, AV_TIME_BASE);
-            int64_t now = av_gettime_relative() - ist->start;
+            int64_t now = (av_gettime_relative() - ist->start)*scale + stream_ts_offset;
             if (pts > now)
                 return AVERROR(EAGAIN);
         }