FFmpeg/libavcodec/wma_common.c

/*
 * common code shared by all WMA variants
 *
 * This file is part of Libav.
 *
 * Libav is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * Libav is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with Libav; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include "libavutil/attributes.h"
#include "wma_common.h"

/**
 *@brief Get the samples per frame for this stream.
 *@param sample_rate output sample_rate
 *@param version wma version
 *@param decode_flags codec compression features
 *@return log2 of the number of output samples per frame
 */
av_cold int ff_wma_get_frame_len_bits(int sample_rate, int version,
                                      unsigned int decode_flags)
{

    int frame_len_bits;

    if (sample_rate <= 16000) {
        frame_len_bits = 9;
    } else if (sample_rate <= 22050 ||
             (sample_rate <= 32000 && version == 1)) {
        frame_len_bits = 10;
    } else if (sample_rate <= 48000 || version < 3) {
        frame_len_bits = 11;
    } else if (sample_rate <= 96000) {
        frame_len_bits = 12;
    } else {
        frame_len_bits = 13;
    }

    if (version == 3) {
        int tmp = decode_flags & 0x6;
        if (tmp == 0x2) {
            ++frame_len_bits;
        } else if (tmp == 0x4) {
            --frame_len_bits;
        } else if (tmp == 0x6) {
            frame_len_bits -= 2;
        }
    }

    return frame_len_bits;
}