[FFmpeg-devel] [PATCH] Add ATRAC3+ decoder

[Paul B Mahol]

On 10/10/13, Maxim Polijakowski <max_pole at gmx.de> wrote:
> Hi crews,
>
> the attached patch adds an open-source decoder for Sony's ATRAC3+
> format. There is a partial description of its internals located here:
> http://wiki.multimedia.cx/index.php?title=ATRAC3plus
>
> Samples: http://samples.mplayerhq.hu/A-codecs/ATRAC3+/
>
> Because the patch is huge, I expect several review rounds.
>
> Therefore, I would like to kindly ask you to sort your review comments
> according to the following priority list:
> --> functionality improvements (code refractions resulting in faster or
> smaller code)
> --> security improvements (code refractions resulting in more secure code)
> --> cosmetic improvements (grammar, spelling etc.)
>
> Any help regarding fuzzy testing and pointing out insecure code would be
> very appreciated!
>
> Thank you in advance!
> Best regards
> Maxim
>


> From e425cb32249a9044c773f0c26ee8f231b818a470 Mon Sep 17 00:00:00 2001
> From: Maxim Poliakovski <max_pole at gmx.de>
> Date: Thu, 10 Oct 2013 20:32:14 +0200
> Subject: [PATCH 1/2] ATRAC+ decoder
>
> Cleanup by Diego Biurrun.
> ---
>  Changelog                    |    1 +
>  configure                    |    1 +
>  doc/general.texi             |    1 +
>  libavcodec/Makefile          |    3 +
>  libavcodec/allcodecs.c       |    1 +
>  libavcodec/atrac3plus.c      | 1735 +++++++++++++++++++++++++++++++++++++
>  libavcodec/atrac3plus.h      |  183 ++++
>  libavcodec/atrac3plus_data.c | 1940 ++++++++++++++++++++++++++++++++++++++++++
>  libavcodec/atrac3plus_data.h |  144 ++++
>  libavcodec/atrac3plusdec.c   |  394 +++++++++
>  libavcodec/atrac3plusdsp.c   |  658 ++++++++++++++
>  libavcodec/version.h         |    2 +-
>  12 files changed, 5062 insertions(+), 1 deletion(-)
>  create mode 100644 libavcodec/atrac3plus.c
>  create mode 100644 libavcodec/atrac3plus.h
>  create mode 100644 libavcodec/atrac3plus_data.c
>  create mode 100644 libavcodec/atrac3plus_data.h
>  create mode 100644 libavcodec/atrac3plusdec.c
>  create mode 100644 libavcodec/atrac3plusdsp.c
>

[...]

> +    const uint8_t *buf  = avpkt->data;
> +    int buf_size        = avpkt->size;
> +    ATRAC3PContext *ctx = avctx->priv_data;
> +    AVFrame *frame      = data;
> +    int i, ret, ch_unit_id, ch_block = 0, out_ch_index = 0, channels_to_process;
> +    float **samples_p = (float **)frame->extended_data;
> +
> +    frame->nb_samples = ATRAC3P_FRAME_SAMPLES;
> +    if ((ret = ff_get_buffer(avctx, frame, 0)) < 0) {
> +        av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
> +        return ret;
> +    }
> +
> +    init_get_bits(&ctx->gb, buf, buf_size * 8);

if ((ret = init_get_bits8(&ctx->gb, avpkt->data, avpkt->size)) < 0)
    return ret;

> +
> +    if (get_bits1(&ctx->gb)) {
> +        av_log(avctx, AV_LOG_ERROR, "Invalid start bit!\n");
> +        return AVERROR_INVALIDDATA;
> +    }
> + */

[...]

> +
> +/**
> + *  @file
> + *  DSP functions for ATRAC3+ decoder.
> + */
> +
> +#include <math.h>
> +
> +#include "libavutil/float_dsp.h"
> +#include "avcodec.h"
> +#include "sinewin.h"
> +#include "fft.h"
> +#include "atrac3plus.h"
> +#include "atrac3plus_data.h"
> +
> +#define ATRAC3P_MDCT_SIZE (ATRAC3P_SUBBAND_SAMPLES * 2)
> +
> +static AVFloatDSPContext atrac3p_dsp;

This looks strange and is probably incorrect, it probably should be in
private context.

> +
> +/**
> + * ATRAC3+ uses two different MDCT windows:
> + * - The first one is just the plain sine window of size 256.
> + * - The 2nd one is the plain sine window of size 128
> + *   wrapped into zero (at the start) and one (at the end) regions.
> + *   Both regions are 32 samples long. */
> +static float mdct_wind_steep[128]; ///< second MDCT window
> +

[...]