Re: Re: help using ac3 encode

Paul Curtis wrote:
> lee wrote:
> 
>>
>>  I"ve made two attempts to use the ac3 encoder, but
>>  neither worked.  I need help.  I tried using
>>  ffmpeg on a 6 channel ogg file and several 6 channel
>>  wave files, e.g.
>>      ffmpeg -i canyon.ogg -acodec ac3 -ab 128 ca.ac3
>>  then played back the resulting ac3 files using
>>  "ac3dec -6 ca.ac3", for this example.  It sounded pretty
>>  bad, missing all the low frequencies, for one thing.
> 
> 
> I have been encoding 5.1 AC3 files by using the '-ac 6' parameter for 
> the encode.
> 
> The channel order should be:
> left, right, center, left rear, right rear, LFE.

Thanks.  I just tried adding "-ac 6" and using a wave file with the
channel order you give.  It made no real difference -- very, very
low quality results with little bass and no discernible surround
effect, though some sound does come from 5 of my speakers.

Maybe this is as good as it gets.  I'm not complaining -- just
trying to make sure I'm doing it right.  Here's a log of my
test:

$ ffmpeg -i amb-ac3.wav -acodec ac3 -ac 6 -ab 128 amb.ac3

Re: Re: help using ac3 encode

Greg Lee wrote:

> Thanks.  I just tried adding "-ac 6" and using a wave file with the
> channel order you give.  It made no real difference -- very, very
> low quality results with little bass and no discernible surround
> effect, though some sound does come from 5 of my speakers.
> 
> $ ffmpeg -i amb-ac3.wav -acodec ac3 -ac 6 -ab 128 amb.ac3
> ffmpeg version 0.4.9-pre1, build 4721, Copyright (c) 2000-2004 Fabrice 
> Bellard
>   built on Aug 15 2004 05:51:54, gcc: 3.2.2
> Input #0, wav, from 'amb-ac3.wav':
>   Duration: 00:03:41.2, bitrate: 4233 kb/s
>   Stream #0.0: Audio: pcm_s16le, 44100 Hz, 5:1, 4233 kb/s
> Output #0, ac3, to 'amb.ac3':
>   Stream #0.0: Audio: ac3, 44100 Hz, 5:1, 128 kb/s
> Stream mapping:
>   Stream #0.0 -> #0.0
> Press [q] to stop encoding
> size=    3449kB time=221.3 bitrate= 127.7kbits/s
> video:0kB audio:3449kB global headers:0kB muxing overhead 0.000000%

Ouch .... 128kb for 6 channels of audio? With a very similar command 
line, I get good audio across all six channels. I do, however, use 448kb 
for the AC3 encoder's bitrate. If possible, you might want to look at 
the incoming WAV file and see what the levels are on each of the six 
channels. On Linux, I use audacity for this as it has nice waveform 
displays for each of the channels.

Regards,

help for ffmpeg use

Re: Compilation troubles on Solaris 9 SPARC

On Tue, Aug 31, 2004 at 11:57:59PM +0200, Moritz Kiese wrote:
> Greetings,
> 
> I have some troubles compiling ffmpeg-0.4.9-pre1 on Solaris 9 SPARC 
> (Blade 1000):
> 
> When linking libavcodec.so I get:
> 
> [... Table with approx 17000 text relocations ...]
> 
> ld: fatal: relocations remain against allocatable but non-writable 
> sections

  I think this is generic, not SPARC/Solaris speficic. For some reason,
  PIC is never added to the actual FLAGS. You could try and manually add
  -fPIC to the config.mak's FLAGS. It works for me.

Thanks,
Roman.

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Write a sentence or date on image captured

I wrote:

> Hi all.
>
> I have modificated the apiexample.c and now it capture image from
> /dev/video0 and create
> JPEGs with libavcodec correctly.
>
> But my problem is the next :
>       I'm using PIX_FMT_YUV_420P (because it use ffmpeg?) and I need
write
> "date" on the
>       image capture (before create JPEG). This date is a string with
color
> "rgb" but I don't Know
>       How write this directly on image?
>       Someone can help me,please?
>
>       Is necesary capture the image with PIX_FMT_RGB24  , write date and
> img_convert this image to
>       YUV other time? or is possible write date directly on image without
> img_convert?
>
> Thanks.
>

Michel Bardiaux wrote:

>>How do you create the image with *just* the date string in the first
place?

I don't understand very well your question but I think you want know
how I write the date string over image before create jpeg?

If it is correct, I situated over the image captured (ppm) and I write the
date sentence with font8x8.h but it function if image captured is RGB
and I'm not sure how do it with YUV image, but now I have a idea.

Have you got any idea to do it?

Thanks.

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Re: Compilation troubles on Solaris 9 SPARC

Moritz Kiese wrote:

> Greetings,
>
> I have some troubles compiling ffmpeg-0.4.9-pre1 on Solaris 9 SPARC 
> (Blade 1000):
>
> When linking libavcodec.so I get:
>
> [... Table with approx 17000 text relocations ...]
>
> ld: fatal: relocations remain against allocatable but non-writable 
> sections
> collect2: ld returned 1 exit status
> make: *** [libavcodec.so] Error 1
>
Ohh yes, I have seen this problem in compilation of N projects on 
Solaris. Most probably this problem will be solved by compiling 
statically. Since ld is creeping, most probably it does not find 
relocations in libavcode.so.

-Veeresh

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How to get th lib of libavcodec for windows?

	I mainly use h264decoder of libavcode.If I compile libavcodec under windows,how to get the lib of
libavcodec ? Can you give me some advises and guidance?
		Thanks!	

　　　　　　　　seven
　　　　　　　　wujianseven <at> hotmail.com
　　　　　　　　　　2004-09-01

Re: help for ffmpeg use

satendra pal singh wrote:

>   
> Hi everyone,
> 
>     i am new here in the list, i am doing studies. i need help for the usage of FFMPEG for H.264 decoder. and the
various options available. My problem is i want to change the format of an H.264 format file generated
using reference encoder JM85 to a YUV file, but i am not able to get the required. i have gone through the
FFMPEG documentation, but cant solve this.
> 
> i have used followig option
> 
> ffmpeg -vcodec h264 -i test.264 test.yuv
> 
> thanx for the help.
> 
> Satendra
> 
What's the output? What is wrong about test.yuv?

--

-- 
Michel Bardiaux
Peaktime Belgium S.A.  Bd. du Souverain, 191  B-1160 Bruxelles
Tel : +32 2 790.29.41

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Re: Write a sentence or date on image captured

sergio.anez <at> telvent.abengoa.com wrote:

> I wrote:
> 
> 
>>Hi all.
>>
>>I have modificated the apiexample.c and now it capture image from
>>/dev/video0 and create
>>JPEGs with libavcodec correctly.
>>
>>But my problem is the next :
>>      I'm using PIX_FMT_YUV_420P (because it use ffmpeg?) and I need
> 
> write
> 
>>"date" on the
>>      image capture (before create JPEG). This date is a string with
> 
> color
> 
>>"rgb" but I don't Know
>>      How write this directly on image?
>>      Someone can help me,please?
>>
>>      Is necesary capture the image with PIX_FMT_RGB24  , write date and
>>img_convert this image to
>>      YUV other time? or is possible write date directly on image without
>>img_convert?
>>
>>Thanks.
>>
> 
> 
> Michel Bardiaux wrote:
> 
> 
>>>How do you create the image with *just* the date string in the first
> 
> place?
> 
> I don't understand very well your question but I think you want know
> how I write the date string over image before create jpeg?
> 
> If it is correct, I situated over the image captured (ppm) and I write the
> date sentence with font8x8.h but it function if image captured is RGB
> and I'm not sure how do it with YUV image, but now I have a idea.
> 
> Have you got any idea to do it?
> 
> Thanks.
> 
What exactly do you mean by *write*? What function do you call?

--

-- 
Michel Bardiaux
Peaktime Belgium S.A.  Bd. du Souverain, 191  B-1160 Bruxelles
Tel : +32 2 790.29.41

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Re: Re: help using ac3 encode

On Wed, 2004-09-01 at 03:17, Paul Curtis wrote:

> Ouch .... 128kb for 6 channels of audio? With a very similar command 
> line, I get good audio across all six channels. I do, however, use 448kb 
> for the AC3 encoder's bitrate. 

Even for two channel audio commercial DVD's use a bitrate of at least
320 Kbps.

I've noticed more often that people tend to think ac3 is a "better"
codec than mp3 so you'd get away with a lower bitrate which obviously is
not true (on the matter of compression rate).

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