From 9d8bb0318a0bc59a04c71555a3c575f8146eab41 Mon Sep 17 00:00:00 2001 From: Mike Melanson Date: Wed, 2 Dec 2009 04:06:27 +0000 Subject: [PATCH] Small refactoring: Instead of 4 loops for decoding AC coefficients based on their grouping, create one loop that indexes into a table of AC VLC tables. There is also a small optimization here: Do not call unpack_vlcs() if there are no fragments in the list with outstanding coefficients. My profiling indicates that this can save upwards of 1 million dezicycles per frame throughout the course of unpack_dct_coeffs(). Originally committed as revision 20699 to svn://svn.ffmpeg.org/ffmpeg/trunk --- libavcodec/vp3.c | 47 +++++++++++++++++++++-------------------------- 1 file changed, 21 insertions(+), 26 deletions(-) diff --git a/libavcodec/vp3.c b/libavcodec/vp3.c index 292f010..cdf8e00 100644 --- a/libavcodec/vp3.c +++ b/libavcodec/vp3.c @@ -1163,6 +1163,8 @@ static int unpack_dct_coeffs(Vp3DecodeContext *s, GetBitContext *gb) int ac_y_table; int ac_c_table; int residual_eob_run = 0; + VLC *y_tables[64]; + VLC *c_tables[64]; /* fetch the DC table indexes */ dc_y_table = get_bits(gb, 4); @@ -1192,40 +1194,33 @@ static int unpack_dct_coeffs(Vp3DecodeContext *s, GetBitContext *gb) ac_y_table = get_bits(gb, 4); ac_c_table = get_bits(gb, 4); - /* unpack the group 1 AC coefficients (coeffs 1-5) */ + /* build tables of AC VLC tables */ for (i = 1; i <= 5; i++) { - residual_eob_run = unpack_vlcs(s, gb, &s->ac_vlc_1[ac_y_table], i, - 1, residual_eob_run); - - residual_eob_run = unpack_vlcs(s, gb, &s->ac_vlc_1[ac_c_table], i, - 0, residual_eob_run); + y_tables[i] = &s->ac_vlc_1[ac_y_table]; + c_tables[i] = &s->ac_vlc_1[ac_c_table]; } - - /* unpack the group 2 AC coefficients (coeffs 6-14) */ for (i = 6; i <= 14; i++) { - residual_eob_run = unpack_vlcs(s, gb, &s->ac_vlc_2[ac_y_table], i, - 1, residual_eob_run); - - residual_eob_run = unpack_vlcs(s, gb, &s->ac_vlc_2[ac_c_table], i, - 0, residual_eob_run); + y_tables[i] = &s->ac_vlc_2[ac_y_table]; + c_tables[i] = &s->ac_vlc_2[ac_c_table]; } - - /* unpack the group 3 AC coefficients (coeffs 15-27) */ for (i = 15; i <= 27; i++) { - residual_eob_run = unpack_vlcs(s, gb, &s->ac_vlc_3[ac_y_table], i, - 1, residual_eob_run); - - residual_eob_run = unpack_vlcs(s, gb, &s->ac_vlc_3[ac_c_table], i, - 0, residual_eob_run); + y_tables[i] = &s->ac_vlc_3[ac_y_table]; + c_tables[i] = &s->ac_vlc_3[ac_c_table]; } - - /* unpack the group 4 AC coefficients (coeffs 28-63) */ for (i = 28; i <= 63; i++) { - residual_eob_run = unpack_vlcs(s, gb, &s->ac_vlc_4[ac_y_table], i, - 1, residual_eob_run); + y_tables[i] = &s->ac_vlc_4[ac_y_table]; + c_tables[i] = &s->ac_vlc_4[ac_c_table]; + } + + /* decode all AC coefficents */ + for (i = 1; i <= 63; i++) { + if (s->fragment_list_y_head != -1) + residual_eob_run = unpack_vlcs(s, gb, y_tables[i], i, + 1, residual_eob_run); - residual_eob_run = unpack_vlcs(s, gb, &s->ac_vlc_4[ac_c_table], i, - 0, residual_eob_run); + if (s->fragment_list_c_head != -1) + residual_eob_run = unpack_vlcs(s, gb, c_tables[i], i, + 0, residual_eob_run); } return 0; -- 2.7.4