[FFmpeg-devel] [PATCH] Bitstream filter DTS from any format to 14bit format.

[Måns Rullgård]

Bartlomiej Wolowiec <bartek.wolowiec at gmail.com> writes:

> Hi,
> Here is a small bitstream filter, which may be useful for someone.
> -- 
> Bartlomiej Wolowiec
>

[...]

> +static int dts14b_filter(AVBitStreamFilterContext * bsfc,
> +                         AVCodecContext * avctx, const char *args,
> +                         uint8_t ** poutbuf, int *poutbuf_size,
> +                         const uint8_t * buf, int buf_size, int keyframe)
> +{
> +    GetBitContext gb;
> +    int dca_buffer_size;
> +    uint8_t dca_buffer[DCA_MAX_FRAME_SIZE];
> +    uint16_t *pout;
> +
> +    dca_buffer_size =
> +        ff_dca_convert_bitstream(buf, buf_size, dca_buffer,
> +                                 DCA_MAX_FRAME_SIZE);
> +    if (dca_buffer_size == -1) {
> +        av_log(avctx, AV_LOG_ERROR, "Not a valid DCA frame\n");
> +        return -1;
> +    }
> +
> +    *poutbuf_size = ((dca_buffer_size + 13) / 14) << 4;
> +    *poutbuf = av_malloc(*poutbuf_size + FF_INPUT_BUFFER_PADDING_SIZE);
> +    pout = (uint16_t *) * poutbuf;

Doesn't gcc complain about strict aliasing violations here?

> +    init_get_bits(&gb, dca_buffer, dca_buffer_size);
> +    while (get_bits_count(&gb) < dca_buffer_size << 3) {
> +        uint16_t tmp = get_bits(&gb, 14);
> +        if (tmp > 0x1FFF)
> +            tmp |= 0xC000;

get_sbits()

> +        *(pout++) = be2me_16(tmp);

Useless ()

> +    }
> +
> +    while (((uint8_t *) pout - *poutbuf) & 7)
> +        *(pout++) = 0;

What's all this padding for?

> +
> +    return 0;
> +}
> +
> +AVBitStreamFilter dts14b_bsf = {
> +    "dts14b",
> +    0,
> +    dts14b_filter,
> +};

-- 
M?ns Rullg?rd
mans at mansr.com