8 audio channels

[scharette]

Hey there,

First of all, I just started to use FFAStrans and it's fantastic !

I'm trying to transcode a quicktime files with 8 channels of audio. I'm using a custom FFmpeg and I haven't find a codec that allowed me to use 8 channels of audio. It's either only transcoding the first 2 channels or it's downmixing all the channels from the original file.

Any idea which codec would allow me to do this ?

Thanks !

[admin]

Hi scharette and thanks for using FAStrans

What are your desired output video format and audio layout? To you want 8 discrete mono tracks or one track with 8 channels?

-steipal

[scharette]

Hey Steipal,

Here is what I'm trying to accomplish.

Our video servers in one location produce quicktime files with Avid DNX145 as the video codec and uncompressed audio with 8 mono channels. At the other location, they will trancode it to XDCam HD422 for their servers.

I need to transfer these files from one location to the other. The bandwidth is limited so I'm trying to transcode the files to another codec for the transport but I would like to keep all 8 audio channels and also the timecode from the original quicktime.

I tried the MP4 encoder. Video look good, file size is great but I'm only able to get 2 channels of audio.

I also tried using custom FFmpeg as the encoder. I did use h264 as the video codec and .mov as the extention, that part did work great. For the audio codec, I tried mp3 and aac and I was not able to preserve the 8 audios channels. I tried others codecs but I couldn't figured how to get it working.

If you have a suggestion, that would be great !

Thanks for your time !

Sebastien

[admin]

Try this custom ffmpeg:

"-map 0 -c:v libx264 -c:a aac -strict -2 -dn -timecode %m_tc_start%"

You can deselect audio and video codec in the gui as we define this in the argument section. You can also experiment with video and audio bitrate like this:

"-map 0 -c:v libx264 -b:v 10000k -c:a aac -b:a 128k -strict -2 -dn -strict -2 -timecode %m_tc_start%"

-steipal

[scharette]

Your software is truly incredible ! I've work with many transcoders and yours is very stable and reliable !

The part for transcoding my files from Avid DNx to H264 with my 8 audios channels did work great.

Now, I have to transcode some files back from H264 to Avid DNx145. The video part work great, but the audio doesn't work so well. I don't know how to explain it, but everything end up in the first 2 channels and not sounding correctly. When I open the file in a software, like VLC, it work great. But when I open it in my hardware (EVS server), it doesn't work properly.

I did 2 screens shots, one of a file that is working,

Working.png (199.53 KiB) Viewed 15242 times

and the one after being transcoded with FFAStrans.

NotWorking.png (201.08 KiB) Viewed 15242 times

I also tried to use FFmpeg to encode DNx and it didn't work. I used dnxhd for the video codec, I'm not sure if this is the correct setting,

Thanks for all your help !

[scharette]

Update : I've figured how to use FFmpeg to encode a Quicktime with DNx with FFMpeg, I've used these options

-map 0:0 -map 0:1 -map 0:2 -map 0:3 -map 0:4 -map 0:5 -map 0:6 -map 0:7 -map 0:8 -c:v dnxhd -b:v 145M -c:a pcm_s24le -flags +ildct -timecode %m_tc_start%

I can't test the file with my server until Thursday but I think I'm getting closer.

I'll keep you posted,

Thanks again !

[admin]

I'm really happy you enjoy my program!

Maybe it's a matter of adding support for 24 bit audio in the "DNxHD" encoder, which should be trivial. I will do that for the next release. Thanks for keeping me posted.

-steipal

[scharette]

I'm trying to get FFmpeg to do a video file with 8 mono audios streams.

I used A/V media and ChannelMapper so this way I always get the same input to FFmpeg. I tried -map and -mapchannel but I can't figure how to take that 7.1 stream coming from ChannelMapper and split it in 8 mono streams. Here's what I thought would work,

-map 0:0 -map 0:1 -map 0:2 -map 0:3 -map 0:4 -map 0:5 -map 0:6 -map 0:7 -map 0:8 -c:v dnxhd -b:v 145M -c:a pcm_s24le -flags +ildct -timecode %m_tc_start%

Also, when I do a H264, the input for my workflow is interlaced files. When I look at the quicktime information it end up being progressive. Since in the end it will be converted back to XDCam interlace, I would like to keep the interlace format without any conversion to progressive. We're using top field first. Here's what I used,

-map 0 -c:v libx264 -b:v 3500k -c:a aac -b:a 128k -strict -2 -dn -strict -2 -timecode %m_tc_start% -pix_fmt yuv420p

Thanks for all your help !

[admin]

Hi, sorry about the delayed answer but this really dodged my radar.

Try this:

"-map 0:1 -map_channel 0.1.0:0.1 -map 0:1 -map_channel 0.1.1:0.2 -map 0:1 -map_channel 0.1.2:0.3 -map 0:1 -map_channel 0.1.3:0.4 -map 0:1 -map_channel 0.1.4:0.5 -map 0:1 -map_channel 0.1.5:0.6 -map 0:1 -map_channel 0.1.6:0.7 -map 0:1 -map_channel 0.1.7:0.8"

This will map 8 channels from the first audio stream to 8 separate mono streams.

As for interlaced x264, try adding "-x264opts tff=1" to your command line.

-steipal

[mrazik]

Hi gents,

it is possible to do the same with standard FFAStrans processors or do I just need to use Custom ffmpeg processor?

Cheers,
mrazik