ffmpeg error when encoding 6 channel aac

[BrianAtVH]

Clip: http://www.dvdloc8.com/clip.php?movieid=13599&clipid=4
258Kbps, 6 channel AAC audio

I'm getting an error when running:
ffmpeg.exe -v verbose -i "c:\IAmLegend.mp4" -vn -ac 6 -ar 48000 -ab 192k -y "c:\test.aac"

[libvo_aacenc @ 03B66900] Unable to set encoding parameters
Error while opening encoder for output stream #0:0 - maybe incorrect parameters such as bit_rate, rate, width or height

The command works with -ac 2. Why is it forcing me to down mix to two channels? I'm running ffmpeg N-34549-g13b7781

[poisondeathray]

I'm getting an error when running:
ffmpeg.exe -v verbose -i "c:\IAmLegend.mp4" -vn -ac 6 -ar 48000 -ab 192k -y "c:\test.aac"

Don't you have to specify -acodec something? perhaps -acodec libvo_aacenc ?

[BrianAtVH]

Nope, ffmpeg will determine the codec based on the output extension

[poisondeathray]

But you can compile ffmpeg with different AAC encoders... how does it know to choose libvo_aacenc over libfaac for example ?

PS. I don't bother using either, because the quality is very poor compared to qaac or even nero

[BrianAtVH]

Apparently, -acodec copy works. Any idea what's going on?

Here's the result without specifying the codec:

Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'c:\IAmLegend.mp4':
Metadata:
major_brand : isom
minor_version : 1
compatible_brands: isom
creation_time : 2008-12-01 05:16:01
Duration: 00:02:03.24, start: 0.000000, bitrate: 8236 kb/s
Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1920x816 [SAR 1:1 DAR 40:17], 7979 kb/s, 23.98 fps, 23.98 tbr, 2500k tbn, 47.95 tbc
Metadata:
creation_time : 2008-12-01 04:50:08
handler_name : GPAC ISO Video Handler
Stream #0:1(und): Audio: aac (mp4a / 0x6134706D), 48000 Hz, 5.1, s16, 258 kb/s
Metadata:
creation_time : 2008-12-01 05:16:04
handler_name : GPAC ISO Audio Handler
[libvo_aacenc @ 033E6900] Unable to set encoding parameters
Output #0, adts, to 'c:\test.aac':
Metadata:
major_brand : isom
minor_version : 1
compatible_brands: isom
creation_time : 2008-12-01 05:16:01
Stream #0:0(und): Audio: aac, 48000 Hz, 6 channels, s16, 96 kb/s
Metadata:
creation_time : 2008-12-01 05:16:04
handler_name : GPAC ISO Audio Handler
Stream mapping:
Stream #0:1 -> #0:0 (aac -> libvo_aacenc)
Error while opening encoder for output stream #0:0 - maybe incorrect parameters such as bit_rate, rate, width or height



Here is the result with -acodec copy (this encodes successfully):

Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'c:\IAmLegend.mp4':
Metadata:
major_brand : isom
minor_version : 1
compatible_brands: isom
creation_time : 2008-12-01 05:16:01
Duration: 00:02:03.24, start: 0.000000, bitrate: 8236 kb/s
Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1920x816 [SAR 1:1 DAR 40:17], 7979 kb/s, 23.98 fps, 23.98 tbr, 2500k tbn, 47.95 tbc
Metadata:
creation_time : 2008-12-01 04:50:08
handler_name : GPAC ISO Video Handler
Stream #0:1(und): Audio: aac (mp4a / 0x6134706D), 48000 Hz, 5.1, s16, 258 kb/s
Metadata:
creation_time : 2008-12-01 05:16:04
handler_name : GPAC ISO Audio Handler
Output #0, adts, to 'c:\test.aac':
Metadata:
major_brand : isom
minor_version : 1
compatible_brands: isom
creation_time : 2008-12-01 05:16:01
encoder : Lavf53.19.0
Stream #0:0(und): Audio: aac (mp4a / 0x6134706D), 48000 Hz, 5.1, 258 kb/s
Metadata:
creation_time : 2008-12-01 05:16:04
handler_name : GPAC ISO Audio Handler
Stream mapping:
Stream #0:1 -> #0:0 (copy)

[poisondeathray]

Apparently, -acodec copy works. Any idea what's going on?

-acodec copy doesn't call the encoder, that's the difference (it just stream copies the audio, not re-encode the audio)

maybe libvo_aacenc doesn't support 5.1 ?