From 3a163db8106e2a36b48d265ae9f2b3a6f60f14cf Mon Sep 17 00:00:00 2001
From: Anton Khirnov <anton@khirnov.net>
Date: Fri, 10 May 2013 09:29:44 +0200
Subject: libav decoder plugin: improve timestamps handling

Make sure the timestamps start at zero.
---
 src/decoder/libav_decoder_plugin.c | 34 +++++++++++++++++++++++-----------
 1 file changed, 23 insertions(+), 11 deletions(-)

diff --git a/src/decoder/libav_decoder_plugin.c b/src/decoder/libav_decoder_plugin.c
index eaeecd60..c27a4187 100644
--- a/src/decoder/libav_decoder_plugin.c
+++ b/src/decoder/libav_decoder_plugin.c
@@ -54,6 +54,11 @@ typedef struct LibavDecContext {
     AVIOContext *io;
     AVFormatContext *fmt_ctx;
     AVStream *ast;
+
+    /* offset to be added to timestamps so they start at 0 */
+    int64_t pts_offset;
+    /* pts of the last frame sent to the player */
+    int64_t last_pts;
 } LibavDecContext;
 
 static const struct tag_table libav_tags[] = {
@@ -194,13 +199,6 @@ fail:
     return ret;
 }
 
-static double time_from_libav(int64_t t, const AVRational time_base)
-{
-    assert(t != (int64_t)AV_NOPTS_VALUE);
-
-    return (double)av_rescale_q(t, time_base, (AVRational){1, 1024}) / (double)1024;
-}
-
 static int64_t time_to_libav(double t, const AVRational time_base)
 {
     return av_rescale_q((int64_t)(t * 1024), (AVRational){1, 1024}, time_base);
@@ -212,9 +210,6 @@ static enum decoder_command libav_send_packet(LibavDecContext *s,
     AVPacket packet2 = *packet;
     enum decoder_command cmd = DECODE_COMMAND_NONE;
 
-    if (packet->pts != (int64_t)AV_NOPTS_VALUE)
-        decoder_timestamp(decoder, time_from_libav(packet->pts, *time_base));
-
     while (packet2.size > 0 &&
            cmd == DECODE_COMMAND_NONE) {
         AVFrame *frame = av_frame_alloc();
@@ -242,6 +237,22 @@ static enum decoder_command libav_send_packet(LibavDecContext *s,
             continue;
         }
 
+        if (s->pts_offset == AV_NOPTS_VALUE) {
+            s->pts_offset = (frame->pkt_pts == AV_NOPTS_VALUE) ?
+                            0 : -frame->pkt_pts;
+        }
+
+        if (frame->pkt_pts != AV_NOPTS_VALUE) {
+            int64_t timestamp = frame->pkt_pts + s->pts_offset;
+            if (timestamp < s->last_pts) {
+                g_warning("Non-monotonous timestamps: previous %"PRId64
+                          ", current %"PRId64"\n", s->last_pts, timestamp);
+            } else {
+                decoder_timestamp(s->decoder, timestamp * av_q2d(s->ast->time_base));
+                s->last_pts = timestamp;
+            }
+        }
+
         cmd = decoder_data(s->decoder, s->input, frame, s->ast->codec->bit_rate / 1000);
     }
     return cmd;
@@ -249,7 +260,7 @@ static enum decoder_command libav_send_packet(LibavDecContext *s,
 
 static void libav_decode(struct decoder *decoder, struct input_stream *input)
 {
-    LibavDecContext s = { .decoder = decoder };
+    LibavDecContext s = { .decoder = decoder, .pts_offset = AV_NOPTS_VALUE };
     AVCodecContext *dec = NULL;
     const AVCodec *codec;
     struct audio_format audio_format;
@@ -317,6 +328,7 @@ static void libav_decode(struct decoder *decoder, struct input_stream *input)
                               AV_TIME_BASE) < 0)
                 decoder_seek_error(decoder);
             else {
+                s.last_pts = 0;
                 avcodec_flush_buffers(dec);
                 decoder_command_finished(decoder);
             }
-- 
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