I am using this commad to transcode a video with 12000k bitrate to a lower bitrate like 300k.
here is my command: ffmpeg -i 12000.mp4 -movflags faststart -c:v libx264 -x264opts 'keyint=288:min-keyint=24:8x8dct:sliced-threads=0' -deblock 1:1 -flags +loop -b:v 300k -maxrate 300k -bufsize 1000k -tune psnr -vf "scale=-1280:720:flags=spline+full_chroma_inp+full_chroma_int+accurate_rnd+bitexact" -acodec libfdk_aac -b:a 320k -coder 1 -me_range 16 -sc_threshold 42 -bf 10 -q:v 1 -qmin 0 -qmax 35 -trellis 2 -mbtree 1 -mixed-refs 1 -preset veryslow video.mp4 I need the bitrate to be 2000, but after using this command and using media info, I see that bitrate is different from what I specified (2000 for ecample) and there is a nominal bitrate which is what I specified in my command. and during the convert process i get the VBV underflow warning after a short time passes. until that warning hasn't showed up, the bitrate seems to be fine. but after that the bitrate starts to get higher. here is my console output: [libx264 @ 0x20bb0c0] VBV underflow (frame 2992, -20064 bits) [libx264 @ 0x20bb0c0] VBV underflow (frame 2993, -13888 bits) [libx264 @ 0x20bb0c0] VBV underflow (frame 2995, -520 bits) [libx264 @ 0x20bb0c0] VBV underflow (frame 2996, -992 bits) [libx264 @ 0x20bb0c0] VBV underflow (frame 2997, -1320 bits) [libx264 @ 0x20bb0c0] VBV underflow (frame 2998, -9528 bits) [libx264 @ 0x20bb0c0] VBV underflow (frame 2999, -744 bits) [mp4 @ 0x20ba1e0] Starting second pass: moving the moov atom to the beginning of the file frame= 3000 fps= 13 q=-1.0 Lsize= 18665kB time=00:01:00.01 bitrate=2547.9kbits/s video:16252kB audio:2346kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.363480% [libx264 @ 0x20bb0c0] frame I:15 Avg QP:30.80 size: 46683 [libx264 @ 0x20bb0c0] frame P:592 Avg QP:31.14 size: 16537 [libx264 @ 0x20bb0c0] frame B:2393 Avg QP:34.69 size: 2570 [libx264 @ 0x20bb0c0] consecutive B-frames: 0.8% 3.3% 5.4% 9.6% 3.3% 76.2% 0.7% 0.0% 0.6% 0.0% 0.0% [libx264 @ 0x20bb0c0] mb I I16..4: 37.0% 48.8% 14.2% [libx264 @ 0x20bb0c0] mb P I16..4: 9.1% 9.4% 1.0% P16..4: 24.2% 7.5% 5.7% 0.8% 0.1% skip:42.2% [libx264 @ 0x20bb0c0] mb B I16..4: 0.4% 0.2% 0.0% B16..8: 17.9% 4.2% 0.7% direct: 0.9% skip:75.6% L0:37.7% L1:49.0% BI:13.3% [libx264 @ 0x20bb0c0] 8x8 transform intra:46.4% inter:49.8% [libx264 @ 0x20bb0c0] direct mvs spatial:99.9% temporal:0.1% [libx264 @ 0x20bb0c0] coded y,uvDC,uvAC intra: 18.8% 27.9% 7.3% inter: 5.6% 3.5% 0.3% [libx264 @ 0x20bb0c0] i16 v,h,dc,p: 29% 46% 10% 15% [libx264 @ 0x20bb0c0] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 11% 19% 55% 3% 2% 3% 3% 2% 3% [libx264 @ 0x20bb0c0] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 26% 30% 17% 3% 5% 6% 5% 4% 4% [libx264 @ 0x20bb0c0] i8c dc,h,v,p: 65% 20% 8% 6% [libx264 @ 0x20bb0c0] Weighted P-Frames: Y:5.6% UV:4.6% [libx264 @ 0x20bb0c0] ref P L0: 57.1% 15.8% 13.9% 3.3% 2.4% 1.7% 1.3% 0.6% 0.6% 0.8% 0.5% 0.4% 0.4% 0.4% 0.4% 0.3% [libx264 @ 0x20bb0c0] ref B L0: 84.1% 9.0% 2.3% 1.4% 0.6% 0.6% 0.6% 0.2% 0.2% 0.3% 0.2% 0.2% 0.1% 0.1% 0.1% [libx264 @ 0x20bb0c0] ref B L1: 96.4% 3.6% [libx264 @ 0x20bb0c0] kb/s:2218.78 and here is a demo of video: https://streamable.com/e6dbg _______________________________________________ ffmpeg-user mailing list ffmpeg-user@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-user To unsubscribe, visit link above, or email ffmpeg-user-requ...@ffmpeg.org with subject "unsubscribe".