[FFmpeg-devel] [PATCH] lavf: split packets before muxing.

[Clément Bœsch]

On Sat, Dec 08, 2012 at 07:42:11PM +0100, Michael Niedermayer wrote:
> On Fri, Dec 07, 2012 at 03:21:02AM +0100, Clément Bœsch wrote:
> > On Thu, Dec 06, 2012 at 01:51:36PM +0100, Nicolas George wrote:
> > > Le sextidi 16 frimaire, an CCXXI, Clément Bœsch a écrit :
> > > > New version merging the side data back after muxing.
> > > 
> > > Sorry to take the train already rolling (av_packet_*_side_data() are
> > > undocumented): would it not be simpler to copy the packet structure and
> > > adjust the size / split the side data in the copy?
> > > 
> > > I find that schemes like "do X; something; undo X" are usually a bad idea.
> > > 
> > 
> > So something like attached instead?
> > 
> > [...]
> > 
> > -- 
> > Clément B.
> 
> >  mux.c |   20 ++++++++++++++++----
> >  1 file changed, 16 insertions(+), 4 deletions(-)
> > d7b715e6b1ee3bc9b350902795c63b4886a6e871  0001-lavf-split-packets-before-muxing.patch
> > From 8de676cadfdd2cf186d02f83b4decddbec021d8f Mon Sep 17 00:00:00 2001
> > From: =?UTF-8?q?Cl=C3=A9ment=20B=C5=93sch?= <ubitux at gmail.com>
> > Date: Mon, 3 Dec 2012 23:13:53 +0100
> > Subject: [PATCH] lavf: split packets before muxing.
> > 
> > After demuxing, data and side are merged. Before decoding, they are
> > split. Encoder will perform with data and side split. This means that a
> > muxer can receive split data (after encoding) but also merged data (if
> > called directly after demuxing). This commit makes sure data and side
> > are split for the muxer.
> > ---
> >  libavformat/mux.c | 20 ++++++++++++++++----
> >  1 file changed, 16 insertions(+), 4 deletions(-)
> > 
> > diff --git a/libavformat/mux.c b/libavformat/mux.c
> > index 9bcee99..f7bb3ad 100644
> > --- a/libavformat/mux.c
> > +++ b/libavformat/mux.c
> > @@ -484,13 +484,25 @@ static int compute_pkt_fields2(AVFormatContext *s, AVStream *st, AVPacket *pkt)
> >      return 0;
> >  }
> >  
> > +static inline int split_write_packet(AVFormatContext *s, AVPacket *pkt)
> > +{
> > +    int ret;
> > +    AVPacket spkt = *pkt;
> > +
> > +    av_packet_split_side_data(&spkt);
> > +    ret = s->oformat->write_packet(s, &spkt);
> > +    spkt.data = NULL;
> > +    av_destruct_packet(&spkt);
> 
> doesnt this leak and crash the next muxer if 2 are called on the
> same packet ?
> 

Why would that happen? data pointer is kept verbatim in
av_packet_split_side_data(), and the side data allocated by it will be
destroyed by av_destruct_packet() without touching the original data
pointer (spkt.data=NULL).

Anything I'm missing?

[...]

-- 
Clément B.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 490 bytes
Desc: not available
URL: <http://ffmpeg.org/pipermail/ffmpeg-devel/attachments/20121219/3bd3cfa7/attachment.asc>