[FFmpeg-devel] [PATCH v2 04/11] avformat/muxers: Add non-blocking mode support for av_write_trailer

[Michael Niedermayer]

On Mon, Aug 22, 2016 at 04:27:16PM +0200, Jan Sebechlebsky wrote:
> 
> 
> On 08/22/2016 09:51 AM, Michael Niedermayer wrote:
> >On Thu, Aug 11, 2016 at 02:38:29PM +0200, sebechlebskyjan at gmail.com wrote:
> >>From: Jan Sebechlebsky <sebechlebskyjan at gmail.com>
> >>
> >>This makes av_write_trailer not to free the resources if write_trailer
> >>call returns AVERROR(EAGAIN) allowing repeated calls of write_trailer of
> >>non-blocking muxer.
> >>
> >>Signed-off-by: Jan Sebechlebsky <sebechlebskyjan at gmail.com>
> >>---
> >>  Changes since the last version of the patch:
> >>  - Added assert to the part of the code dealing with flushing
> >>    interleaved packets which should not be entered if
> >>    muxer in non-blocking mode is used.
> >>    (also there is assert for the same condition added into
> >>     av_interleaved_write_packet in one of the following
> >>     patches).
> >>
> >>  libavformat/avformat.h |  6 +++++-
> >>  libavformat/mux.c      | 10 ++++++++--
> >>  2 files changed, 13 insertions(+), 3 deletions(-)
> >>
> >>diff --git a/libavformat/avformat.h b/libavformat/avformat.h
> >>index d8a6cf3..2cc3156 100644
> >>--- a/libavformat/avformat.h
> >>+++ b/libavformat/avformat.h
> >>@@ -2510,8 +2510,12 @@ int av_write_uncoded_frame_query(AVFormatContext *s, int stream_index);
> >>   *
> >>   * May only be called after a successful call to avformat_write_header.
> >>   *
> >>+ * If AVFMT_FLAG_NONBLOCK is set, this call may return AVERROR(EAGAIN)
> >>+ * meaning the operation is pending and the call should be repeated.
> >>+ *
> >>   * @param s media file handle
> >>- * @return 0 if OK, AVERROR_xxx on error
> >>+ * @return 0 if OK, AVERROR(EAGAIN) in case call should be repeated,
> >>+ *         other AVERROR on error
> >>   */
> >>  int av_write_trailer(AVFormatContext *s);
> >>diff --git a/libavformat/mux.c b/libavformat/mux.c
> >>index e9973ed..3ae924c 100644
> >>--- a/libavformat/mux.c
> >>+++ b/libavformat/mux.c
> >>@@ -1204,11 +1204,14 @@ int av_write_trailer(AVFormatContext *s)
> >>      for (;; ) {
> >>          AVPacket pkt;
> >>          ret = interleave_packet(s, &pkt, NULL, 1);
> >>-        if (ret < 0)
> >>-            goto fail;
> >>          if (!ret)
> >>              break;
> >>+        av_assert0(!(s->flags & AVFMT_FLAG_NONBLOCK));
> >this would abort on any error not just EAGAIN
> I think it will abort in case interleave_packets does not return 0
> from the first call in loop, which means that interleaving was used
> (because there are some packets to be flushed) and that situation
> cannot happen with AVFMT_FLAG_NONBLOCK set when interleaving is
> forbidded. The next patch also adds assert to
> av_interleaved_write_packet. But I think the assert here is on the
> right place, or have I misunderstood the problem you're pointing
> out?

I thought interleave_packet can return AVERROR(ENOMEM)
maybe this is not possible, still it seems non-robust to assert if
it errors out

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Opposition brings concord. Out of discord comes the fairest harmony.
-- Heraclitus
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 181 bytes
Desc: Digital signature
URL: <http://ffmpeg.org/pipermail/ffmpeg-devel/attachments/20160822/75c56ec7/attachment.sig>