Some question about surround audio track and stereo audio track

[Neroldy]

I have some question about sorround audio track and stereo audio track these days, so I want to ask about it. And I'm sorry for my bad English.

1. For audio listening, I just use my laptop and JBL PEBBLES Stereo voice box, and does it make sense to use AC-3 5.1(640K) instead of AC-3 2.0(640K/448K/384K)? Does it will be better for stereo playback using sorround audio track?
2. I want to convert AC-3 5.1(640K) to AC-3 2.0 to just keep the stereo part of original audio file using eac3to, what bitrate should I decide? I don't want to increase bitrate unless it is useful for the audio file. I use eac3to like this command:
eac3to "original_audio(640K).ac3" "audio.ac3" -down2
and the bitrate of audio.ac3 is 448K, does this result tell me that in the sorround audio track(640K/5.1), the stereo part is 448K?

:thanks:

[tebasuna51]

1) Nope. Use stereo.

2) For AC3 2.0 the eac3to default bitrate is 448 Kb/s, but is enough 256 Kb/s. Use:

eac3to "original_audio(640K).ac3" "audio.ac3" -downStereo -256

[Neroldy]

1) Nope. Use stereo.

2) For AC3 2.0 the eac3to default bitrate is 448 Kb/s, but is enough 256 Kb/s. Use:

eac3to "original_audio(640K).ac3" "audio.ac3" -downStereo -256

Thank you~ :thanks:

[kuchikirukia]

1. You're downmixing, not "extracting the stereo."

2. Why would you transcode to something as old as AC-3? Use QAAC --tvbr 91.