How does ffmpeg determine individual stream bitrates

bitrateffmpegvideo

For example, I have a video for which ffmpeg shows

  Duration: 00:46:43.72, start: 0.540000, bitrate: 2593 kb/s
    Stream #0.0[0x1e0]: Video: mpeg2video (Main), yuv420p, 720x576 [PAR 16:15 DAR 4:3], 9000 kb/s, 25 fps, 25 tbr, 90k tbn, 50 tbc
    Stream #0.1[0x80]: Audio: ac3, 48000 Hz, stereo, s16, 448 kb/s

The size of the file is 908843008 bytes, so the 2593 kb/s is correct. But why does it say that the video stream bitrate is 9000 kb/s?

Best Answer

MPEG streams typically use variable bitrate encoding in order to save space in sections of the video that are easy to encode, thus allow increased quality. FFMpeg is reporting the bitrate stored in the video stream's sequence header, which is the maximum bitrate in the entire file (or, in many cases, the maximum bitrate the encoder was configured to allow -- the actual file may not have any sections that use as high a bitrate as this). The value 9000kbps is typical of MPEG2 streams from (or destined for) DVDs: DVDs have a maximum combined video & audio bitrate of 9800kbps, so this allows ~500kbps for audio and some spare for navigation packets & other overhead.

Related Solutions

Set MP4 thumbnail

Try to use ffmpeg -disposition option along with -map.

ffmpeg -i video.mp4 -i image.png -map 0 -map 1 -c copy -c:v:1 png -disposition:v:1 attached_pic out.mp4

More information can be found in ffmpeg documentation:

Also, please note, it's not guaranteed that the image you use will be showed in a video preview or as a file tumbanail, because different software programs may not use embedded thumbnails at all.

Linux – Using ffmpeg to make a movie from png files

This is the wrong syntax for passing multiple images as input to ffmpeg. Please have a look at the FFmpeg Wiki guide on creating a video slideshow and the image2 demuxer options.

You need to tell it to use three digits for the sequence numbers, and start at 84, i.e.

ffmpeg -start_number 84 -i island_sizes-CSH\(II\)-%03d.png output.mpg

Some further tips:

MPEG-1 as a video codec is less than optimal and gives you bad quality at high file sizes. Unless you want compatibility for old devices or computers (or Windows XP without any codecs), scratch that and use an MPEG-4 Part 10 encoder (H.264), such as libx264:
```
ffmpeg -i … -c:v libx264 out.mp4
```
For a tutorial on x264 options (how to change the quality etc.) check the x264 encoding guide.
PNG files use an RGB pixel format, which is not supported in normal video codecs. With MPEG-1 it does not matter, but with MPEG-4 codecs it would, since ffmpeg would automatically convert the pixel format to non-subsampled YUV. In that case you need to translate this to chroma-subsampled formats such as YUV 4:2:0, otherwise your video might not play in most applications:
```
ffmpeg -i … -c:v libx264 -pix_fmt yuv420p out.mp4
```

Best Answer

Related Solutions

Set MP4 thumbnail

Linux – Using ffmpeg to make a movie from png files

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