[FFmpeg-devel] [PATCH] avcodec/alsdec: implement floating point decoding
Michael Niedermayer
michael at niedermayer.cc
Thu Jul 21 15:48:30 EEST 2016
On Sun, Jul 17, 2016 at 12:06:03AM +0530, Umair Khan wrote:
> Hi,
>
> Patch attached.
>
> - Umair
> libavcodec/Makefile | 2
> libavcodec/alsdec.c | 284 +++++++++++++++++++++++++++++++++++++++++-
> libavcodec/mlz.c | 171 +++++++++++++++++++++++++
> libavcodec/mlz.h | 69 ++++++++++
> libavutil/softfloat_ieee754.h | 115 +++++++++++++++++
> 5 files changed, 638 insertions(+), 3 deletions(-)
> 0282267108d74681f1bff6b5e6a85c603ac7052e 0001-avcodec-alsdec-implement-floating-point-decoding.patch
> From 70e65b26cc3f84c9c664c30808b43a5e1cf16eaa Mon Sep 17 00:00:00 2001
> From: Umair Khan <omerjerk at gmail.com>
> Date: Sat, 16 Jul 2016 23:52:39 +0530
> Subject: [PATCH 1/1] avcodec/alsdec: implement floating point decoding
>
> It conforms to RM22 version of the reference codec.
>
> Signed-off-by: Umair Khan <omerjerk at gmail.com>
> ---
> libavcodec/Makefile | 2 +-
> libavcodec/alsdec.c | 284 +++++++++++++++++++++++++++++++++++++++++-
> libavcodec/mlz.c | 171 +++++++++++++++++++++++++
> libavcodec/mlz.h | 69 ++++++++++
> libavutil/softfloat_ieee754.h | 115 +++++++++++++++++
missing update to Changelog
[...]
> @@ -1356,6 +1366,237 @@ static int revert_channel_correlation(ALSDecContext *ctx, ALSBlockData *bd,
> }
>
>
> +/** multiply two softfloats and handle the rounding off
> + */
> +static SoftFloat_IEEE754 multiply(SoftFloat_IEEE754 a, SoftFloat_IEEE754 b) {
> + uint64_t mantissa_temp;
> + uint64_t mask_64;
> + int bit_count;
> + int cutoff_bit_count;
> + unsigned char last_2_bits;
> + unsigned int mantissa;
> + uint32_t return_val = 0;
> + int32_t sign;
> +
> + sign = a.sign ^ b.sign;
> +
> + // Multiply mantissa bits in a 64-bit register
> + mantissa_temp = (uint64_t)a.mant * (uint64_t)b.mant;
> +
> + // Count the valid bit count
> + for (bit_count=48, mask_64=(uint64_t)0x1 << 47; !(mantissa_temp & mask_64) && mask_64; bit_count--, mask_64>>=1);
this needs some newlines for readability
> +
> + // Round off
> + cutoff_bit_count = bit_count - 24;
> + if (cutoff_bit_count > 0) {
> + last_2_bits = (unsigned char)(((unsigned int)mantissa_temp >> (cutoff_bit_count - 1)) & 0x3 );
> + if ((last_2_bits == 0x3) || ((last_2_bits == 0x1) && ((unsigned int)mantissa_temp & ((0x1UL << (cutoff_bit_count - 1)) - 1)))) {
> + // Need to round up
> + mantissa_temp += (uint64_t)0x1 << cutoff_bit_count;
> + }
> + }
> +
> + mantissa = (unsigned int)(mantissa_temp >> cutoff_bit_count);
> +
> + // Need one more shift?
> + if (mantissa & 0x01000000ul) {
> + bit_count++;
> + mantissa >>= 1;
> + }
> +
> + if (!sign) {
> + return_val = 0x80000000U;
> + }
> +
> + return_val |= (a.exp + b.exp + bit_count - 47) << 23;
> + return_val |= mantissa;
> + return av_bits2sf_ieee754(return_val);
> +}
> +
> +
> +/** Read and decode the floating point sample data
> + */
> +static int read_diff_float_data(ALSDecContext *ctx, unsigned int ra_frame) {
> + AVCodecContext *avctx = ctx->avctx;
> + GetBitContext *gb = &ctx->gb;
> + SoftFloat_IEEE754 *acf = ctx->acf;
> + int *shift_value = ctx->shift_value;
> + int *last_shift_value = ctx->last_shift_value;
> + int *last_acf_mantissa = ctx->last_acf_mantissa;
> + int **raw_mantissa = ctx->raw_mantissa;
> + int *nbits = ctx->nbits;
> + unsigned char *larray = ctx->larray;
> + int frame_length = ctx->cur_frame_length;
> + SoftFloat_IEEE754 scale = av_int2sf_ieee754(0x1u, 23);
> + unsigned int partA_flag;
> + unsigned int highest_byte;
> + unsigned int shift_amp;
> + uint32_t tmp_32;
> + int use_acf;
> + int nchars;
> + int i;
> + int c;
> + long k;
> + long nbits_aligned;
> + unsigned long acc;
> + unsigned long j;
> + uint32_t sign;
> + uint32_t e;
> + uint32_t mantissa;
> +
> + skip_bits_long(gb, 32); //num_bytes_diff_float
> + use_acf = get_bits1(gb);
> +
> + if (ra_frame) {
> + for (c = 0; c < avctx->channels; ++c) {
> + last_acf_mantissa[c] = 0;
> + last_shift_value[c] = 0;
> + }
memset()
> + ff_mlz_flush_dict(ctx->mlz);
> + }
> +
> + for (c = 0; c < avctx->channels; ++c) {
> + if (use_acf) {
> + //acf_flag
> + if (get_bits1(gb)) {
> + tmp_32 = get_bits(gb, 23);
> + last_acf_mantissa[c] = tmp_32;
> + } else {
> + tmp_32 = last_acf_mantissa[c];
> + }
> + acf[c] = av_bits2sf_ieee754(tmp_32);
> + } else {
> + acf[c] = FLOAT_1;
> + }
> +
> + highest_byte = get_bits(gb, 2);
> + partA_flag = get_bits1(gb);
> + shift_amp = get_bits1(gb);
> +
> + if (shift_amp) {
> + shift_value[c] = get_bits(gb, 8);
> + last_shift_value[c] = shift_value[c];
> + } else {
> + shift_value[c] = last_shift_value[c];
> + }
> +
> + if (partA_flag) {
> + if (!get_bits1(gb)) { //uncompressed
> + for (i = 0; i < frame_length; ++i) {
> + if (ctx->raw_samples[c][i] == 0) {
> + ctx->raw_mantissa[c][i] = get_bits_long(gb, 32);
> + }
> + }
> + } else { //compressed
> + nchars = 0;
> + for (i = 0; i < frame_length; ++i) {
> + if (ctx->raw_samples[c][i] == 0) {
> + nchars += 4;
> + }
> + }
> +
> + tmp_32 = ff_mlz_decompression(ctx->mlz, gb, nchars, larray);
> + if(tmp_32 != nchars) {
> + av_log(ctx->avctx, AV_LOG_ERROR, "Error in MLZ decompression (%d, %d).\n", tmp_32, nchars);
> + return AVERROR_INVALIDDATA;
> + }
> +
> + for (i = 0; i < frame_length; ++i) {
> + tmp_32 = (larray[i] << 24) | larray[i+1] << 16 | larray[i+2] << 8 | larray[i+3];
AV_RB32()
> + ctx->raw_mantissa[c][i] = tmp_32;
> + }
> + }
> + }
> +
> + //decode part B
> + if (highest_byte) {
> + for (i = 0; i < frame_length; ++i) {
> + if (ctx->raw_samples[c][i] != 0) {
> + //The following logic is taken from Tabel 14.45 and 14.46 from the ISO spec
> + if (av_cmp_sf_ieee754(acf[c], FLOAT_1)) {
> + nbits[i] = 23 - av_log2(abs(ctx->raw_samples[c][i]));
> + } else {
> + nbits[i] = 23;
> + }
> + nbits[i] = FFMIN(nbits[i], highest_byte*8);
> + }
> + }
> +
> + if (!get_bits1(gb)) { //uncompressed
> + for (i = 0; i < frame_length; ++i) {
> + if (ctx->raw_samples[c][i] != 0) {
> + raw_mantissa[c][i] = get_bits(gb, nbits[i]);
> + }
> + }
> + } else { //compressed
> + nchars = 0;
> + for (i = 0; i < frame_length; ++i) {
> + if (ctx->raw_samples[c][i]) {
> + nchars += (int) nbits[i] / 8;
> + if (nbits[i] % 8 > 0) {
can nbits[] be < 0 ?
if not then &7 is better than %8
[...]
> +static int decode_string(MLZDict *dict, unsigned char *buff, int string_code, int *first_char_code, unsigned long bufsize) {
> + unsigned long count, offset;
> + int current_code, parent_code, tmp_code;
> +
> + count = 0;
> + current_code = string_code;
> + *first_char_code = CODE_UNSET;
> +
> + while (count < bufsize) {
> + switch (current_code) {
> + case CODE_UNSET:
> + return count;
> + break;
> + default:
> + if (current_code < FIRST_CODE) {
> + *first_char_code = current_code;
> + buff[0] = current_code;
> + count++;
> + return count;
> + } else {
> + offset = dict[current_code].match_len - 1;
> + tmp_code = dict[current_code].char_code;
> + buff[offset] = tmp_code;
> + count++;
> + }
> + current_code = dict[current_code].parent_code;
> + if ((current_code < 0) || (current_code > (DIC_INDEX_MAX - 1))) {
> + av_log(NULL, AV_LOG_ERROR, "MLZ dic index error.\n");
it would be ideal if all av_log() would have a context instead of NULL
[...]
--
Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
If you fake or manipulate statistics in a paper in physics you will never
get a job again.
If you fake or manipulate statistics in a paper in medicin you will get
a job for life at the pharma industry.
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