[vlc-devel] [PATCH 1/2] DASH: implement Seek()

[Frederic YHUEL]

On Wed, Mar 28, 2012 at 6:06 PM, Hugo Beauzée-Luyssen
<beauze.h at gmail.com> wrote:
>
> 2012/3/26 Frédéric Yhuel <fyhuel at viotech.net>:
> > This is needed for DASH module to work with (not yet ready) VLC MP4
> > demux. Forward seeking is implemented by calling Read() with a NULL
> > argument (= skipping), while backward seeking is limited to the current
> > block in the block_bytestream_t upon which is built the internal buffer.
> > This limitation is not really a problem because backward seeking will be
> > needed only for the parsing of the initialization fragment.
> > ---
> >  modules/stream_filter/dash/DASHManager.cpp        |    5 ++
> >  modules/stream_filter/dash/DASHManager.h          |    1 +
> >  modules/stream_filter/dash/buffer/BlockBuffer.cpp |   16 ++++++
> >  modules/stream_filter/dash/buffer/BlockBuffer.h   |    1 +
> >  modules/stream_filter/dash/dash.cpp               |   53
> > ++++++++++++++++++++-
> >  5 files changed, 74 insertions(+), 2 deletions(-)
> >
> > diff --git a/modules/stream_filter/dash/DASHManager.cpp
> > b/modules/stream_filter/dash/DASHManager.cpp
> > index f649015..8483c9d 100644
> > --- a/modules/stream_filter/dash/DASHManager.cpp
> > +++ b/modules/stream_filter/dash/DASHManager.cpp
> > @@ -74,6 +74,11 @@ int     DASHManager::read( void *p_buffer, size_t len
> > )
> >     return this->buffer->get(p_buffer, len);
> >  }
> >
> > +int     DASHManager::seekBackwards( unsigned i_len )
> > +{
> > +    return this->buffer->seekBackwards( i_len );
> > +}
> > +
> >  int     DASHManager::peek( const uint8_t **pp_peek, size_t i_peek )
> >  {
> >     return this->buffer->peek(pp_peek, i_peek);
> > diff --git a/modules/stream_filter/dash/DASHManager.h
> > b/modules/stream_filter/dash/DASHManager.h
> > index a09e98e..90d9317 100644
> > --- a/modules/stream_filter/dash/DASHManager.h
> > +++ b/modules/stream_filter/dash/DASHManager.h
> > @@ -47,6 +47,7 @@ namespace dash
> >             bool    start   ();
> >             int     read    ( void *p_buffer, size_t len );
> >             int     peek    ( const uint8_t **pp_peek, size_t i_peek );
> > +            int     seekBackwards ( unsigned len );
> >
> >             const mpd::IMPDManager*         getMpdManager   () const;
> >             const logic::IAdaptationLogic*  getAdaptionLogic() const;
> > diff --git a/modules/stream_filter/dash/buffer/BlockBuffer.cpp
> > b/modules/stream_filter/dash/buffer/BlockBuffer.cpp
> > index 056c481..1db9168 100644
> > --- a/modules/stream_filter/dash/buffer/BlockBuffer.cpp
> > +++ b/modules/stream_filter/dash/buffer/BlockBuffer.cpp
> > @@ -85,6 +85,22 @@ int     BlockBuffer::peek                 (const
> > uint8_t **pp_peek, unsigned int
> >     vlc_mutex_unlock(&this->monitorMutex);
> >     return ret;
> >  }
> > +
> > +int     BlockBuffer::seekBackwards       (unsigned len)
> > +{
> > +    vlc_mutex_lock(&this->monitorMutex);
> > +    if( this->buffer.i_offset > len )
> > +    {
> > +        this->buffer.i_offset -= len;
> > +        this->sizeBytes += len;
> > +        vlc_mutex_unlock(&this->monitorMutex);
> > +        return VLC_SUCCESS;
> > +    }
> > +
> > +    vlc_mutex_unlock(&this->monitorMutex);
> > +    return VLC_EGENERIC;
> > +}
> > +
> >  int     BlockBuffer::get                  (void *p_data, unsigned int
> > len)
> >  {
> >     vlc_mutex_lock(&this->monitorMutex);
> > diff --git a/modules/stream_filter/dash/buffer/BlockBuffer.h
> > b/modules/stream_filter/dash/buffer/BlockBuffer.h
> > index 570861f..2c39db1 100644
> > --- a/modules/stream_filter/dash/buffer/BlockBuffer.h
> > +++ b/modules/stream_filter/dash/buffer/BlockBuffer.h
> > @@ -49,6 +49,7 @@ namespace dash
> >                 void    put         (block_t *block);
> >                 int     get         (void *p_data, unsigned int len);
> >                 int     peek        (const uint8_t **pp_peek, unsigned
> > int i_peek);
> > +                int     seekBackwards (unsigned len);
> >                 void    setEOF      (bool value);
> >                 bool    getEOF      ();
> >                 mtime_t size        ();
> > diff --git a/modules/stream_filter/dash/dash.cpp
> > b/modules/stream_filter/dash/dash.cpp
> > index b503f27..9003a9d 100644
> > --- a/modules/stream_filter/dash/dash.cpp
> > +++ b/modules/stream_filter/dash/dash.cpp
> > @@ -77,7 +77,7 @@ struct stream_sys_t
> >         dash::DASHManager                   *p_dashManager;
> >         dash::http::HTTPConnectionManager   *p_conManager;
> >         dash::mpd::MPD                      *p_mpd;
> > -        int                                 position;
> > +        uint64_t                            position;
> >         bool                                isLive;
> >  };
> >
> > @@ -160,6 +160,46 @@ static void Close(vlc_object_t *p_obj)
> >
> >  /*****************************************************************************
> >  * Callbacks:
> >
> >  *****************************************************************************/
> > +static int  Seek            ( stream_t *p_stream, uint64_t pos )
> > +{
> > +    stream_sys_t        *p_sys          = (stream_sys_t *)
> > p_stream->p_sys;
> > +    dash::DASHManager   *p_dashManager  = p_sys->p_dashManager;
> > +    int                 i_ret           = 0;
> > +    unsigned            i_len           = 0;
> > +    long                i_read          = 0;
> > +
> > +    if( pos < p_sys->position )
> > +    {
> > +        if( p_sys->position - pos > UINT_MAX )
> > +        {
> > +            msg_Err( p_stream, "Cannot seek backward that far!" );
> > +            return VLC_EGENERIC;
> > +        }
> > +        i_len = p_sys->position - pos;
> You are checking for an UINT overflow, but are assigning into an int.
>

No, i_len is unsigned :-)

Have a good evening,

--
Frédéric