[FFmpeg-devel] [PATCH 01/10] avformat/mux: Only prepare input packet if there is a packet

[Andreas Rheinhardt]

It is unnecessary to call prepare_input_packet if there is no packet as
it doesn't do anything, except when the currently inactive code guarded
by !FF_API_COMPUTE_PKT_FIELDS2 || !FF_API_LAVF_AVCTX becomes active:
Then attempting to access pkt->stream_index will crash.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at gmail.com>
---
This works very well together with Marton's patch #4 [1]:
write_packets_common(): The prepare_input_packet() call can be moved
into write_packets_common(). Unfortunately, it's not compatible with #5
[2] as-is, but I think I have a solution for this.

[1]: https://ffmpeg.org/pipermail/ffmpeg-devel/2020-March/259203.html
[2]: https://ffmpeg.org/pipermail/ffmpeg-devel/2020-March/259204.html

 libavformat/mux.c | 22 ++++++++++------------
 1 file changed, 10 insertions(+), 12 deletions(-)

diff --git a/libavformat/mux.c b/libavformat/mux.c
index bfd1bf491b..814d773b9d 100644
--- a/libavformat/mux.c
+++ b/libavformat/mux.c
@@ -771,9 +771,6 @@ static int write_packet(AVFormatContext *s, AVPacket *pkt)
 
 static int check_packet(AVFormatContext *s, AVPacket *pkt)
 {
-    if (!pkt)
-        return 0;
-
     if (pkt->stream_index < 0 || pkt->stream_index >= s->nb_streams) {
         av_log(s, AV_LOG_ERROR, "Invalid packet stream index: %d\n",
                pkt->stream_index);
@@ -887,10 +884,6 @@ int av_write_frame(AVFormatContext *s, AVPacket *pkt)
 {
     int ret;
 
-    ret = prepare_input_packet(s, pkt);
-    if (ret < 0)
-        return ret;
-
     if (!pkt) {
         if (s->oformat->flags & AVFMT_ALLOW_FLUSH) {
             ret = s->oformat->write_packet(s, NULL);
@@ -902,6 +895,10 @@ int av_write_frame(AVFormatContext *s, AVPacket *pkt)
         return 1;
     }
 
+    ret = prepare_input_packet(s, pkt);
+    if (ret < 0)
+        return ret;
+
     ret = do_packet_auto_bsf(s, pkt);
     if (ret <= 0)
         return ret;
@@ -1191,12 +1188,12 @@ int av_interleaved_write_frame(AVFormatContext *s, AVPacket *pkt)
 {
     int ret, flush = 0;
 
-    ret = prepare_input_packet(s, pkt);
-    if (ret < 0)
-        goto fail;
-
     if (pkt) {
-        AVStream *st = s->streams[pkt->stream_index];
+        AVStream *st;
+
+        ret = prepare_input_packet(s, pkt);
+        if (ret < 0)
+            goto fail;
 
         ret = do_packet_auto_bsf(s, pkt);
         if (ret == 0)
@@ -1209,6 +1206,7 @@ int av_interleaved_write_frame(AVFormatContext *s, AVPacket *pkt)
                 pkt->size, av_ts2str(pkt->dts), av_ts2str(pkt->pts));
 
 #if FF_API_COMPUTE_PKT_FIELDS2 && FF_API_LAVF_AVCTX
+        st = s->streams[pkt->stream_index];
         if ((ret = compute_muxer_pkt_fields(s, st, pkt)) < 0 && !(s->oformat->flags & AVFMT_NOTIMESTAMPS))
             goto fail;
 #endif
-- 
2.20.1