[FFmpeg-devel] [PATCH] libvpx: alt reference frame / lag

[Michael Niedermayer]

On Tue, Jun 08, 2010 at 06:44:42PM -0400, James Zern wrote:
> The attached adds altref to flags2 and uses rc_lookahead for
> g_lag_in_frames mapping.
> Alternate reference frames are currently only produced in 2-pass.
> Further description outside of the API docs [1]. I'm ignoring the alt.
> ref. noise reduction settings for this pass.
> 
> [1]: http://www.webmproject.org/tools/encoder-parameters/#5_the_alternate_or_constructed_reference_frame

>  avcodec.h   |    5 +++--
>  libvpxenc.c |   11 +++++++++++
>  options.c   |    1 +
>  3 files changed, 15 insertions(+), 2 deletions(-)
> 5c3078a90d9d169ab2ceae1622311bec825e8ba9  libvpxenc-altref__lag.diff
> Index: libavcodec/options.c
> ===================================================================
> --- libavcodec/options.c	(revision 23540)
> +++ libavcodec/options.c	(working copy)
> @@ -414,6 +414,7 @@ static const AVOption options[]={
>  {"intra_refresh", "use periodic insertion of intra blocks instead of keyframes", 0, FF_OPT_TYPE_CONST, CODEC_FLAG2_INTRA_REFRESH, INT_MIN, INT_MAX, V|E, "flags2"},
>  {"crf_max", "in crf mode, prevents vbv from lowering quality beyond this point", OFFSET(crf_max), FF_OPT_TYPE_FLOAT, DEFAULT, 0, 51, V|E},
>  {"log_level_offset", "set the log level offset", OFFSET(log_level_offset), FF_OPT_TYPE_INT, 0, INT_MIN, INT_MAX },
> +{"altref", "enable use of alternate reference frames (VP8/2-pass only)", 0, FF_OPT_TYPE_CONST, CODEC_FLAG2_ALT_REF, INT_MIN, INT_MAX, V|E, "flags2"},
>  {NULL},
>  };
>  
> Index: libavcodec/avcodec.h
> ===================================================================
> --- libavcodec/avcodec.h	(revision 23540)
> +++ libavcodec/avcodec.h	(working copy)
> @@ -30,8 +30,8 @@
>  #include "libavutil/avutil.h"
>  
>  #define LIBAVCODEC_VERSION_MAJOR 52
> -#define LIBAVCODEC_VERSION_MINOR 75
> -#define LIBAVCODEC_VERSION_MICRO  1
> +#define LIBAVCODEC_VERSION_MINOR 76
> +#define LIBAVCODEC_VERSION_MICRO  0
>  
>  #define LIBAVCODEC_VERSION_INT  AV_VERSION_INT(LIBAVCODEC_VERSION_MAJOR, \
>                                                 LIBAVCODEC_VERSION_MINOR, \
> @@ -600,6 +600,7 @@ typedef struct RcOverride{
>  #define CODEC_FLAG2_PSY           0x00080000 ///< Use psycho visual optimizations.
>  #define CODEC_FLAG2_SSIM          0x00100000 ///< Compute SSIM during encoding, error[] values are undefined.
>  #define CODEC_FLAG2_INTRA_REFRESH 0x00200000 ///< Use periodic insertion of intra blocks instead of keyframes.
> +#define CODEC_FLAG2_ALT_REF       0x00400000 ///< Allow encoder to insert alternate reference frames (VP8 only)
>  
>  /* Unsupported options :
>   *              Syntax Arithmetic coding (SAC)
> Index: libavcodec/libvpxenc.c
> ===================================================================
> --- libavcodec/libvpxenc.c	(revision 23540)
> +++ libavcodec/libvpxenc.c	(working copy)
> @@ -218,11 +218,21 @@ static av_cold int vp8_init(AVCodecConte
>      }
>      dump_enc_cfg(avctx, &enccfg);
>  
> +    /* With altref set an additional frame at the same pts may be produced.
> +       Increasing the time_base gives the library a window to place these frames
> +       ensuring strictly increasing timestamps. */
> +    if (avctx->flags2 & CODEC_FLAG2_ALT_REF) {
> +        avctx->ticks_per_frame = 2;
> +        avctx->time_base       = av_mul_q(avctx->time_base,
> +                                          (AVRational){1, avctx->ticks_per_frame});
> +    }

this looks and sounds wrong
the way divx/xvid packed b frames are handled is much saner

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

The misfortune of the wise is better than the prosperity of the fool.
-- Epicurus
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