[FFmpeg-devel] [PATCH v2] avformat/fifo: only rescale written packet timestamps once

[Jan Ekström]

From: Jan Ekström <jan.ekstrom at 24i.com>

Flag the message as having been adjusted by setting an unsigned
integer field to nonzero, and by only applying the timestamp
adjustment if it is zero. This way the original values do not have
to be reverted back in case of failure.

Fixes an issue where the timestamp adjustment would be re-done over
and over again in case of output requiring a recovery attempt.

Signed-off-by: Jan Ekström <jan.ekstrom at 24i.com>
---
 libavformat/fifo.c | 22 ++++++++++++++--------
 1 file changed, 14 insertions(+), 8 deletions(-)

diff --git a/libavformat/fifo.c b/libavformat/fifo.c
index 17748e94ce..633cf4d7c3 100644
--- a/libavformat/fifo.c
+++ b/libavformat/fifo.c
@@ -117,6 +117,7 @@ typedef enum FifoMessageType {
 typedef struct FifoMessage {
     FifoMessageType type;
     AVPacket pkt;
+    unsigned int packet_ts_adjusted;
 } FifoMessage;
 
 static int fifo_thread_write_header(FifoThreadContext *ctx)
@@ -176,13 +177,13 @@ static int64_t next_duration(AVFormatContext *avf, AVPacket *pkt, int64_t *last_
     return duration;
 }
 
-static int fifo_thread_write_packet(FifoThreadContext *ctx, AVPacket *pkt)
+static int fifo_thread_write_packet(FifoThreadContext *ctx, AVPacket *pkt,
+                                    unsigned int *packet_ts_adjusted)
 {
     AVFormatContext *avf = ctx->avf;
     FifoContext *fifo = avf->priv_data;
     AVFormatContext *avf2 = fifo->avf;
-    AVRational src_tb, dst_tb;
-    int ret, s_idx;
+    int ret;
 
     if (fifo->timeshift && pkt->dts != AV_NOPTS_VALUE)
         atomic_fetch_sub_explicit(&fifo->queue_duration, next_duration(avf, pkt, &ctx->last_received_dts), memory_order_relaxed);
@@ -198,10 +199,14 @@ static int fifo_thread_write_packet(FifoThreadContext *ctx, AVPacket *pkt)
         }
     }
 
-    s_idx = pkt->stream_index;
-    src_tb = avf->streams[s_idx]->time_base;
-    dst_tb = avf2->streams[s_idx]->time_base;
-    av_packet_rescale_ts(pkt, src_tb, dst_tb);
+    if (!*packet_ts_adjusted) {
+        int s_idx = pkt->stream_index;
+        AVRational src_tb = avf->streams[s_idx]->time_base;
+        AVRational dst_tb = avf2->streams[s_idx]->time_base;
+
+        av_packet_rescale_ts(pkt, src_tb, dst_tb);
+        *packet_ts_adjusted = 1;
+    }
 
     ret = av_write_frame(avf2, pkt);
     if (ret >= 0)
@@ -243,7 +248,8 @@ static int fifo_thread_dispatch_message(FifoThreadContext *ctx, FifoMessage *msg
         av_assert0(ret >= 0);
         return ret;
     case FIFO_WRITE_PACKET:
-        return fifo_thread_write_packet(ctx, &msg->pkt);
+        return fifo_thread_write_packet(ctx, &msg->pkt,
+                                        &msg->packet_ts_adjusted);
     case FIFO_FLUSH_OUTPUT:
         return fifo_thread_flush_output(ctx);
     }
-- 
2.29.2