[FFmpeg-devel] [PATCH v2] avcodec/ac3dec: add a flush callback for the ac3 and eac3 decoders

[Michael Niedermayer]

Hi James

On Thu, Feb 06, 2025 at 04:17:47PM -0300, James Almer wrote:
> Fixes ticket #10732
> 
> Signed-off-by: James Almer <jamrial at gmail.com>
> ---
>  libavcodec/ac3dec.c       | 10 ++++++++++
>  libavcodec/ac3dec.h       | 40 ++++++++++++++++++++++-----------------
>  libavcodec/ac3dec_fixed.c |  1 +
>  libavcodec/ac3dec_float.c |  2 ++
>  4 files changed, 36 insertions(+), 17 deletions(-)
> 
> diff --git a/libavcodec/ac3dec.c b/libavcodec/ac3dec.c
> index ff8cbfb0b4..2cf82abc19 100644
> --- a/libavcodec/ac3dec.c
> +++ b/libavcodec/ac3dec.c
[...]
>  /**
>   * Parse the 'sync info' and 'bit stream info' from the AC-3 bitstream.
>   * GetBitContext within AC3DecodeContext must point to
> diff --git a/libavcodec/ac3dec.h b/libavcodec/ac3dec.h
> index 98de7b5abf..cc6d1a118e 100644
> --- a/libavcodec/ac3dec.h
> +++ b/libavcodec/ac3dec.h
> @@ -75,8 +75,30 @@ typedef struct AC3DecodeContext {
>      AVCodecContext *avctx;                  ///< parent context
>      GetBitContext gbc;                      ///< bitstream reader
>  
> +    AVTXContext *tx_128, *tx_256;
> +    av_tx_fn tx_fn_128, tx_fn_256;
> +
> +///@name Optimization
> +    BswapDSPContext bdsp;
> +#if USE_FIXED
> +    AVFixedDSPContext *fdsp;
> +#else
> +    AVFloatDSPContext *fdsp;
> +#endif
> +    AC3DSPContext ac3dsp;
> +    FmtConvertContext fmt_conv;             ///< optimized conversion functions
> +///@}
> +
> +    INTFLOAT *xcfptr[AC3_MAX_CHANNELS];
> +    INTFLOAT *dlyptr[AC3_MAX_CHANNELS];
> +
> +    AVChannelLayout downmix_layout;
> +    SHORTFLOAT *downmix_coeffs[2];              ///< stereo downmix coefficients
> +
> +// Start of flushable fields
>  ///@name Bit stream information
>  ///@{
> +    // frame_type must be first
>      int frame_type;                         ///< frame type                             (strmtyp)
>      int substreamid;                        ///< substream identification
>      int superframe_size;                    ///< current superframe size, in bytes
> @@ -164,7 +186,6 @@ typedef struct AC3DecodeContext {
>      int fbw_channels;                           ///< number of full-bandwidth channels
>      int channels;                               ///< number of total channels
>      int lfe_ch;                                 ///< index of LFE channel
> -    SHORTFLOAT *downmix_coeffs[2];              ///< stereo downmix coefficients
>      int downmixed;                              ///< indicates if coeffs are currently downmixed
>      int output_mode;                            ///< output channel configuration
>      int prev_output_mode;                       ///< output channel configuration for previous frame
> @@ -222,24 +243,9 @@ typedef struct AC3DecodeContext {
>  
>  ///@name IMDCT
>      int block_switch[AC3_MAX_CHANNELS];     ///< block switch flags                     (blksw)
> -    AVTXContext *tx_128, *tx_256;
> -    av_tx_fn tx_fn_128, tx_fn_256;
> -///@}
> -
> -///@name Optimization
> -    BswapDSPContext bdsp;
> -#if USE_FIXED
> -    AVFixedDSPContext *fdsp;
> -#else
> -    AVFloatDSPContext *fdsp;
> -#endif
> -    AC3DSPContext ac3dsp;
> -    FmtConvertContext fmt_conv;             ///< optimized conversion functions
>  ///@}
>  
>      SHORTFLOAT *outptr[AC3_MAX_CHANNELS];
> -    INTFLOAT *xcfptr[AC3_MAX_CHANNELS];
> -    INTFLOAT *dlyptr[AC3_MAX_CHANNELS];
>  
>  ///@name Aligned arrays
>      DECLARE_ALIGNED(16, int,   fixed_coeffs)[AC3_MAX_CHANNELS][AC3_MAX_COEFS];       ///< fixed-point transform coefficients
> @@ -252,7 +258,7 @@ typedef struct AC3DecodeContext {
>      DECLARE_ALIGNED(32, SHORTFLOAT, output_buffer)[EAC3_MAX_CHANNELS][AC3_BLOCK_SIZE * 6];  ///< final output buffer
>  ///@}
>  
> -    AVChannelLayout downmix_layout;
> +// End of flushable fields
>  } AC3DecodeContext;

This seems moving fields around,
if so, maybe this should be in a seperate patch

thx

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

Breaking DRM is a little like attempting to break through a door even
though the window is wide open and the only thing in the house is a bunch
of things you dont want and which you would get tomorrow for free anyway
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