[Libav-user] Converting from AV_SAMPLE_FMT_FLTP to AV_SAMPLE_FMT_FLT

[fkwatson at aol.com]

From: Taha Ansari <mtaha.ansari at gmail.com>
To: This list is about using libavcodec, libavformat, libavutil, libavdevice
 and libavfilter. <libav-user at ffmpeg.org>
Sent: Sat, Dec 7, 2013 6:00 am
Subject: Re: [Libav-user] Converting from AV_SAMPLE_FMT_FLTP to AV_SAMPLE_FMT_FLT



On Fri, Dec 6, 2013 at 6:21 AM, Alexandru Rosca <srosca at bu.edu> wrote:

I am decoding audio and trying to convert it from the planar format to just FLT (packed?). I am making a library which when used will return the buffer with the data. I am using swr_convert but if I pass it frame.extended_data, it crashes.



Yes, swr_convert functions should be able to do this without any problem.

 

 If I just pass it frame.data[0] I get really crackly audio on the other end. I suspect the problem is converting between these formats? Setting request_sample_fmt to av_sample_flt doesnt work.




You might want to share some workable sample code, otherwise it is pure guessing.





 >>>>>>>


I do not use sws_convert to do this because there is no real conversion necessary, just copying.   Since I have to copy data from frame.data[] anyway, I do a simple copy for non planar format. But with planar format, channel 1's samples are in frame.data[0] and channel 2's samples are in frame.data[1].  You just need to copy the 4-byte samples from the two buffers to your single output buffer interleaved, i.e., channel 1 - sample 0, channel 2 - sample 0, channel 1 - sample 1, channel 2 - sample 1, ...


-Felix






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