1 @TEMPLATE encoder_tmpl.c 2 Two Pass Encoder 3 ================ 4 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ INTRODUCTION 5 This is an example of a two pass encoder loop. It takes an input file in 6 YV12 format, passes it through the encoder twice, and writes the compressed 7 frames to disk in IVF format. It builds upon the simple_encoder example. 8 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ INTRODUCTION 9 10 11 Twopass Variables 12 ----------------- 13 Twopass mode needs to track the current pass number and the buffer of 14 statistics packets. 15 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ TWOPASS_VARS 16 int pass; 17 vpx_fixed_buf_t stats = {0}; 18 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ TWOPASS_VARS 19 20 21 Updating The Configuration 22 --------------------------------- 23 In two pass mode, the configuration has to be updated on each pass. The 24 statistics buffer is passed on the last pass. 25 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ TWOPASS_LOOP_BEGIN 26 for(pass=0; pass<2; pass++) { 27 frame_cnt = 0; 28 29 if(pass == 0) 30 cfg.g_pass = VPX_RC_FIRST_PASS; 31 else { 32 cfg.g_pass = VPX_RC_LAST_PASS; 33 cfg.rc_twopass_stats_in = stats; 34 } 35 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ TWOPASS_LOOP_BEGIN 36 37 38 Encoding A Frame 39 ---------------- 40 Encoding a frame in two pass mode is identical to the simple encoder 41 example, except the deadline is set to VPX_DL_BEST_QUALITY to get the 42 best quality possible. VPX_DL_GOOD_QUALITY could also be used. 43 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ENCODE_FRAME 44 frame_avail = read_frame(infile, &raw); 45 if(vpx_codec_encode(&codec, frame_avail? &raw : NULL, frame_cnt, 46 1, flags, VPX_DL_BEST_QUALITY)) 47 die_codec(&codec, "Failed to encode frame"); 48 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ENCODE_FRAME 49 50 51 Processing Statistics Packets 52 ----------------------------- 53 Each packet of type `VPX_CODEC_CX_FRAME_PKT` contains the encoded data 54 for this frame. We write a IVF frame header, followed by the raw data. 55 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PROCESS_STATS 56 case VPX_CODEC_STATS_PKT: 57 stats.buf = realloc(stats.buf, stats.sz 58 + pkt->data.twopass_stats.sz); 59 if(!stats.buf) 60 die("Memory reallocation failed.\n"); 61 memcpy((char*)stats.buf + stats.sz, 62 pkt->data.twopass_stats.buf, 63 pkt->data.twopass_stats.sz); 64 stats.sz += pkt->data.twopass_stats.sz; 65 break; 66 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PROCESS_STATS 67 68 69 Pass Progress Reporting 70 ----------------------------- 71 It's sometimes helpful to see when each pass completes. 72 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ TWOPASS_LOOP_END 73 printf("Pass %d complete.\n", pass+1); 74 } 75 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ TWOPASS_LOOP_END 76
