[FFmpeg-user] How can I solve multiple audio + video mixing and overlay problem

[Moritz Barsnick]

On Wed, Apr 08, 2015 at 19:31:50 -0700, Jeromy wrote:
> Stream specifier 'iv6' in filtergraph description
> amix=inputs=6:duration=longest:dropout_transition=6,asplit=2[a1][a2],nullsrc=s=1280x720[base];split=2[iv1][iv2];[iv1][base]overlay=0:0[mid1];[iv2][mid1]overlay=0:0[mid2];[iv3][mid2]overlay=0:0[mid3];[iv4][mid3]overlay=0:0[mid4];[iv5][mid4]overlay=0:0[mid5];[iv6][mid5]overlay=0:0[mid6];[0:v]scale=426x360[iv0];[1:v]scale=426x360[iv1];[2:v]scale=426x360[iv2];[3:v]scale=426x360[iv3];[4:v]scale=426x360[iv4];[5:v]scale=426x360[iv5];[base][iv0]overlay=1[tmp0];[tmp0][iv1]overlay=1:x=426[tmp1];[tmp1][iv2]overlay=1:x=852[tmp2];[tmp2][iv3]overlay=1:y=360[tmp3];[tmp3][iv4]overlay=1:x=426:y=360[tmp4];[tmp4][iv5]overlay=1:x=852:y=360[tmp5]
> matches no streams.
> 
> maybe it`s command problem.

Of course it's a filter command problem. Check your filter argument. At
one point, you use [iv6] as input, but you never create it anywhere:
  [iv6][mid5]overlay=0:0[mid6]

I think this is a very obvious error, and ffmpeg's message is very
clear about this.

A little hint, in case your eyes are too tired: With your six scale
filters, you create iv0..iv5. But in your six overlay filters, you use
iv1..iv6 as inputs. Stop thinking like a computer scientist and always
start counting at 1. ;-) (Or vice versa.)

Moritz