[FFmpeg-devel] [PATCH v2 1/2] avcodec/noise: don't force non-zero value for amount

[Michael Niedermayer]

On Sat, Jul 24, 2021 at 01:24:54AM +0530, Gyan Doshi wrote:
> 
> 
> On 2021-07-24 01:14, Michael Niedermayer wrote:
> > On Fri, Jul 23, 2021 at 04:04:49PM +0530, Gyan Doshi wrote:
> > > Currently, the user is forced to accept some noise in
> > > packet payload, even if not requested.
> > > ---
> > >   doc/bitstream_filters.texi                    | 13 +++++-------
> > >   libavcodec/noise_bsf.c                        | 21 +++++++++++++------
> > >   tests/fate/matroska.mak                       |  2 +-
> > >   .../fate/matroska-mastering-display-metadata  | 10 ++++-----
> > >   4 files changed, 26 insertions(+), 20 deletions(-)
> > > 
> > > diff --git a/doc/bitstream_filters.texi b/doc/bitstream_filters.texi
> > > index d10842ae47..2b84bda1fc 100644
> > > --- a/doc/bitstream_filters.texi
> > > +++ b/doc/bitstream_filters.texi
> > > @@ -534,20 +534,17 @@ container. Can be used for fuzzing or testing error resilience/concealment.
> > >   Parameters:
> > >   @table @option
> > >   @item amount
> > > -A numeral string, whose value is related to how often output bytes will
> > > -be modified. Therefore, values below or equal to 0 are forbidden, and
> > > -the lower the more frequent bytes will be modified, with 1 meaning
> > > -every byte is modified.
> > > +Accepts a positive integer. Lower the value, more frequently bytes will be modified,
> > > +with @var{1} meaning every byte is modified. Default is @var{0}.
> > >   @item dropamount
> > > -A numeral string, whose value is related to how often packets will be dropped.
> > > -Therefore, values below or equal to 0 are forbidden, and the lower the more
> > > -frequent packets will be dropped, with 1 meaning every packet is dropped.
> > > +Accepts a positive integer. Lower the value, more frequently packets will be dropped,
> > > +with @var{1} meaning every packet is dropped. Default is @var{0}.
> > >   @end table
> > >   The following example applies the modification to every byte but does not drop
> > >   any packets.
> > >   @example
> > > -ffmpeg -i INPUT -c copy -bsf noise[=1] output.mkv
> > > +ffmpeg -i INPUT -c copy -bsf noise=amount=1 output.mkv
> > >   @end example
> > >   @section null
> > > diff --git a/libavcodec/noise_bsf.c b/libavcodec/noise_bsf.c
> > > index 6ebd369633..c1b0203442 100644
> > > --- a/libavcodec/noise_bsf.c
> > > +++ b/libavcodec/noise_bsf.c
> > > @@ -33,20 +33,28 @@ typedef struct NoiseContext {
> > >       unsigned int state;
> > >   } NoiseContext;
> > > -static int noise(AVBSFContext *ctx, AVPacket *pkt)
> > > +static int noise_init(AVBSFContext *ctx)
> > >   {
> > >       NoiseContext *s = ctx->priv_data;
> > > -    int amount = s->amount > 0 ? s->amount : (s->state % 10001 + 1);
> > > -    int i, ret;
> > you are droping the support for variable noise
> > 
> > this also breaks a simple plain "-bsf noise"
> 
> Will re-add it. Is making it default required?

what else would -bsf noise do ?
I think someone using "-bsf noise" might be surprised if what it does changes
Is there a disadvantge in leaving the default ?

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

In a rich man's house there is no place to spit but his face.
-- Diogenes of Sinope
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