conda build requirement: add package from specific channel

Question

Is it possible to add to a conda recipe a build requirement that comes from a specific binstar channel?

For instance I want to create a recipe for ffmpeg-devel, which requires 7zip. But it seems only 7za from the trent channel works. I tried to put trent/7za or trent 7za but neither of them work.

package:
name: ffmpeg-dev
version: 2.3.3

source:
fn: ffmpeg-20140827-git-8c1b942-win64-dev.7z
url: http://ffmpeg.zeranoe.com/builds/win64/dev/ffmpeg-20140827-git-8c1b942-win64-dev.7z [win]
sha1: 1aaf45274229cba7fe723a4118ca243e77cb4587

requirements:
build:
    - trent/7za
    - ffmpeg-dev
run:
    - ffmpeg-dev

about:
home: https://www.ffmpeg.org/
license: "Various (see Copyright file from the aspell6-en source)"
summary: "A complete, cross-platform solution to record, convert and stream au

Answer 1

This is not yet possible, but it is a feature we want to add. For now, you need to add the channels to your configuration before you build, like

conda config --add channels trent 

Answer 2

I think nowadays this syntax may be possible:

trent::7za