From 6c8e85c66074cdd687c0c63754c15911e46abc9b Mon Sep 17 00:00:00 2001 From: Andreas Rheinhardt Date: Fri, 30 Oct 2020 02:27:15 +0100 Subject: [PATCH] avcodec/mpc8: Reduce the size of some VLCs Several of the quantisation VLCs come in pairs and up until now the number of bits used for each VLC was set to the same value for both VLCs in such a pair even when one of the two required only a lower number. This is a waste given that the get_vlc2() call is compatible with these two VLCs using a different number of bits (it uses vlc->bits). Given that the code lengths are descending it is easily possible to know the length of the longest code for a given VLC: It is the length of the first one. With this information one can easily use the least amount of bits. Signed-off-by: Andreas Rheinhardt --- libavcodec/mpc8.c | 22 +++++++++++----------- 1 file changed, 11 insertions(+), 11 deletions(-) diff --git a/libavcodec/mpc8.c b/libavcodec/mpc8.c index c599d34326..2744bcbac1 100644 --- a/libavcodec/mpc8.c +++ b/libavcodec/mpc8.c @@ -87,10 +87,10 @@ static int mpc8_get_mask(GetBitContext *gb, int size, int t) } static const uint16_t vlc_offsets[13] = { - 0, 640, 1184, 1748, 2298, 2426, 2554, 3066, 3578, 4106, 4618, 5196, 5708 + 0, 640, 1184, 1748, 2298, 2426, 2490, 3002, 3258, 3786, 4298, 4876, 5388 }; -static av_cold void build_vlc(VLC *vlc, int nb_bits, +static av_cold void build_vlc(VLC *vlc, const uint8_t codes_counts[16], const uint8_t syms[], int offset) { @@ -101,7 +101,7 @@ static av_cold void build_vlc(VLC *vlc, int nb_bits, for (unsigned tmp = num + codes_counts[i - 1]; num < tmp; num++) len[num] = i; - ff_init_vlc_from_lengths(vlc, nb_bits, num, len, 1, + ff_init_vlc_from_lengths(vlc, FFMIN(len[0], 9), num, len, 1, syms, 1, 1, offset, INIT_VLC_USE_NEW_STATIC, NULL); } @@ -112,7 +112,7 @@ static av_cold int mpc8_decode_init(AVCodecContext * avctx) GetBitContext gb; static int vlc_initialized = 0; int channels; - static VLC_TYPE codes_table[5708][2]; + static VLC_TYPE codes_table[5388][2]; if(avctx->extradata_size < 2){ av_log(avctx, AV_LOG_ERROR, "Too small extradata size (%i)!\n", avctx->extradata_size); @@ -150,7 +150,7 @@ static av_cold int mpc8_decode_init(AVCodecContext * avctx) static VLC_TYPE table[static_size][2]; \ (vlc)->table = table; \ (vlc)->table_allocated = static_size; \ - build_vlc(vlc, bits, len_counts, symbols, offset); \ + build_vlc(vlc, len_counts, symbols, offset); \ } while (0) @@ -180,29 +180,29 @@ static av_cold int mpc8_decode_init(AVCodecContext * avctx) for(i = 0; i < 2; i++){ res_vlc[i].table = &codes_table[vlc_offsets[0+i]]; res_vlc[i].table_allocated = vlc_offsets[1+i] - vlc_offsets[0+i]; - build_vlc(&res_vlc[i], MPC8_RES_BITS, + build_vlc(&res_vlc[i], mpc8_res_len_counts[i], mpc8_res_syms[i], 0); q2_vlc[i].table = &codes_table[vlc_offsets[2+i]]; q2_vlc[i].table_allocated = vlc_offsets[3+i] - vlc_offsets[2+i]; - build_vlc(&q2_vlc[i], MPC8_Q2_BITS, + build_vlc(&q2_vlc[i], mpc8_q2_len_counts[i], mpc8_q2_syms[i], 0); quant_vlc[0][i].table = &codes_table[vlc_offsets[4+i]]; quant_vlc[0][i].table_allocated = vlc_offsets[5+i] - vlc_offsets[4+i]; - build_vlc(&quant_vlc[0][i], MPC8_Q5_BITS, + build_vlc(&quant_vlc[0][i], mpc8_q5_len_counts[i], mpc8_q5_syms[i], MPC8_Q5_OFFSET); quant_vlc[1][i].table = &codes_table[vlc_offsets[6+i]]; quant_vlc[1][i].table_allocated = vlc_offsets[7+i] - vlc_offsets[6+i]; - build_vlc(&quant_vlc[1][i], MPC8_Q6_BITS, + build_vlc(&quant_vlc[1][i], mpc8_q6_len_counts[i], mpc8_q6_syms[i], MPC8_Q6_OFFSET); quant_vlc[2][i].table = &codes_table[vlc_offsets[8+i]]; quant_vlc[2][i].table_allocated = vlc_offsets[9+i] - vlc_offsets[8+i]; - build_vlc(&quant_vlc[2][i], MPC8_Q7_BITS, + build_vlc(&quant_vlc[2][i], mpc8_q7_len_counts[i], mpc8_q7_syms[i], MPC8_Q7_OFFSET); quant_vlc[3][i].table = &codes_table[vlc_offsets[10+i]]; quant_vlc[3][i].table_allocated = vlc_offsets[11+i] - vlc_offsets[10+i]; - build_vlc(&quant_vlc[3][i], MPC8_Q8_BITS, + build_vlc(&quant_vlc[3][i], mpc8_q8_len_counts[i], mpc8_q8_syms[i], MPC8_Q8_OFFSET); } vlc_initialized = 1;