ffmpeg prints out inconsistent transcoding stats for multiple outputs

[Wang Cao]

Summary of the bug:
After transcoding, for multiple output with when two outputs are specified, output 0 has size of 100 kB and output 1 has size of 50 kB, ffmpeg prints something like:

frame=  206 fps=3.6 q=0.0 LPSNR=Y:45.57 U:50.04 V:50.07 *:46.62 size=    100kB time=00:00:07.10 bitrate=1362.7kbits/s speed=0.124x
video:140kB audio:79kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.382502%

video:140kB size is not consistent with the size reported to the previous line because it is an aggregation of all output streams.

This behavior should be reproducible for any inputs to produce multiple outputs.

How to reproduce:

% ffmpeg -i <input> -y output0 -y output1

Proposal:
Add an option to print stats for each outputs. Keep the original prints so that people are not surprised with the previous behavior for now. The new behavior would be something like:

video:50kB audio:38kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.382502%
video:50kB audio:38kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.382502%