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LoRd_MuldeR · 18th April 2015, 21:24

First of all: Why do you worry so much about this? The bitrate of a video stream is almost always not a fixed thing anyway! It's fluctuating constantly. So if we talk about "the bitrate" of a video stream, what we actually mean is the stream's average bitrate. And, even in 2-Pass mode, x264 does not hit the target (average) bitrate perfectly accurate. If, e.g., you encode with a target bitrate of 515 kbps, you will almost certainly end with a slightly higher or lower average bitrate.

Code:

Creating encoder process:
x264_8bit_x64.exe --bitrate 515 --pass 2 --stats city.704x576.stats --output city.704x576.264 city.704x576.avi

ffms [info]: 704x576p 0:1 @ 60062/1001 fps (vfr)
x264 [info]: using cpu capabilities: MMX2 SSE2Fast SSSE3 Cache64 SlowShuffle
x264 [info]: profile High, level 3.1
[...]
encoded 600 frames, 92.02 fps, 514.07 kb/s
Final file size is 627.5 KB bytes.

Secondly: Why do the programs show different bitrate? Reasons I can think of include different rounding strategies ("round to nearest" vs. "truncation") when rounding from bits/s to kilobits/s. It is also quite possible that the one program simply shows the "nominal" bitrate, as stored in the fil'se header, while the other program computes the actual average bitrate of the stream. As we have seen above, this is not necessarily the same...

18th April 2015, 21:24	#2 \| Link
LoRd_MuldeR Software Developer Join Date: Jun 2005 Location: Last House on Slunk Street Posts: 13,248	First of all: Why do you worry so much about this? The bitrate of a video stream is almost always not a fixed thing anyway! It's fluctuating constantly. So if we talk about "*the* bitrate" of a video stream, what we actually mean is the stream's average bitrate. And, even in 2-Pass mode, x264 does not hit the target (average) bitrate perfectly accurate. If, e.g., you encode with a target bitrate of 515 kbps, you will almost certainly end with a slightly higher or lower average bitrate. Code: Creating encoder process: x264_8bit_x64.exe --bitrate 515 --pass 2 --stats city.704x576.stats --output city.704x576.264 city.704x576.avi ffms [info]: 704x576p 0:1 @ 60062/1001 fps (vfr) x264 [info]: using cpu capabilities: MMX2 SSE2Fast SSSE3 Cache64 SlowShuffle x264 [info]: profile High, level 3.1 [...] encoded 600 frames, 92.02 fps, 514.07 kb/s Final file size is 627.5 KB bytes. Secondly: Why do the programs show different bitrate? Reasons I can think of include different rounding strategies ("round to nearest" vs. "truncation") when rounding from bits/s to kilobits/s. It is also quite possible that the one program simply shows the "nominal" bitrate, as stored in the fil'se header, while the other program computes the actual average bitrate of the stream. As we have seen above, this is not necessarily the same... __________________ Go to https://standforukraine.com/ to find legitimate Ukrainian Charities 🇺🇦✊ Last edited by LoRd_MuldeR; 19th April 2015 at 00:25.