[FFmpeg-devel] Add waveformat extensible support in wav muxer (SoC qualification task)

[zhentan feng]

Hi

2009/3/27 Benjamin Larsson <banan at ludd.ltu.se>

> zhentan feng wrote:
> > Hi
> >
> > 2009/3/26 Benjamin Larsson <banan at ludd.ltu.se>
> >
> >> zhentan feng wrote:
> >>
> >>> Hi
> >>>
> >>> 2009/3/26 Michael Niedermayer <michaelni at gmx.at>
> >>>
> >>>
> >>>
> >>>> On Thu, Mar 26, 2009 at 01:19:00AM +0800, zhentan feng wrote:
> >>>>
> >>>>
> >>>>> Hi,
> >>>>>
> >>>>> Here is patch for the small task of qualification tasks NO.30.
> >>>>> Based on the work of Benjamin Larsson, I generated the pathc as
> below.
> >>>>>      I think it must need further modifies.
> >>>>>
> >>>>>
> >>>> yes, iam not sure if this or benjamins patch was better
> >>>>
> >>>>
> >>>>
> >>>
> >>> I downloaded the 6-channel wav file from:
> >>>
> >>>
> http://www-mmsp.ece.mcgill.ca/Documents/AudioFormats/WAVE/Samples/Microsoft/6_Channel_ID.wav
> >>>
> >>> ( and other typr wav files can acess here :
> >>> http://www-mmsp.ece.mcgill.ca/Documents/AudioFormats/WAVE/Samples.html)
> >>>
> >>> 1) then I run ./ffmpeg_g -i 6_Channel_ID.wav channel4.wav
> >>>
> >>> I get the error:
> >>> Resampling with input channels greater than 2 unsupported.
> >>>
> >>> so I run another command:
> >>> 2) ./output_example test.wav
> >>> ./ffmpeg_g -i test.wav -ac 4 ch4.wav
> >>>
> >>> and enc->channels is 4, however enc->channel_layout is 0.
> >>>
> >>>
> >>>
> >>> Finally, I have 2 questions:
> >>>
> >>> 1) how to test the muxer works correctly?
> >>>
> >>>
> >> When the muxer works correctly it should be possible to transcode a wav
> >> file that contains the wavformatextensible header.
> >>
> >>  2) where to specify the enc->channel_layout?
> >>>
> >> It should be filled in by ffmpeg.c.
> >>
> >
> > I debug the commandline:
> > ./ffmpeg_g -i test.wav -ac 4 4ch.wav
> >
> > and found that the enc->channel_layout value is assigned from the input
> file
> > channel_layout. In this case, it is 0.
> > and it seems that "-channel_layout" option doesn't work.
> >
> > 1) is it need to refresh the channel_layout value according to the
> channels
> > in ffmpeg.c or in put_wav_header()?
> > 2) any tools to examine the output file is correct?
> >
> > zhentan feng
>
>
> Hi, this is the latest version of my patch. This adds the maybe correct
> GUID values. To really test this you need to find a wav file with a
> corrrect dwChannelMask. And then make sure that the muxer puts the same
> mask to the transcoded file. The output file should also be playable in
> windows.
>
> [...]


1) I download the 6 channels sample wav file form the follow link:
http://www-mmsp.ece.mcgill.ca/Documents/AudioFormats/WAVE/Samples/Microsoft/6_Channel_ID.wav

then acoording to the new patch, I run the command:
./ffmpeg -i 6_Channel_ID.wav output_ch6.wav

the program run normaly, here is the output result.

Input #0, wav, from '6_Channel_ID.wav':
  Duration: 00:00:05.83, bitrate: 4233 kb/s
    Stream #0.0: Audio: pcm_s16le, 44100 Hz, 6 channels
(FL|FR|FC|LFE|BL|BR), s16, 4233 kb/s
Output #0, wav, to 'output_ch6.wav':
    Stream #0.0: Audio: pcm_s16le, 44100 Hz, 6 channels
(FL|FR|FC|LFE|BL|BR), s16, 4233 kb/s
Stream mapping:
  Stream #0.0 -> #0.0
Press [q] to stop encoding
size=    3017kB time=5.84 bitrate=4233.7kbits/s
video:0kB audio:3017kB global headers:0kB muxing overhead 0.002201%

2) The file 6_Channel_ID.wav can be palyed by windows mediaplayer, but the
output_ch6.wav can't.

I compared the two wav files and found that 6_Channel_ID.wav has 60 more
bytes than output_ch6.wav
the 60 bytes are after WAVEFORMATEXTENSIBLE sturct,followed by the data.
Except for the 60 bytes, the two files are all the same.

However, I noticed that the sample website says about 6_Channel_ID.wav that
:"This file has a "cue " chunk with a count of zero cue points, followed by
two empty cue point structures."

my question is:
are the 60 bytes cue chunk? and how to handle this?

zhentan feng
thanks
-- 
Best wishes~