Hi Damon,

I was able to do something similar to what you are describing.  However, instead of building ffmpeg with Alchemy I used the native process feature found in Air 2.0 to interact with ffmpeg.  In short, native process in Air 2.0 allows you to write to stdout and read from stdIn.  FFMPEG also has the ability to listen to take input on stdin "-i -"  and write to stdout.  Furthermore, the the flash.net.NetStream change in Flash version 10.1 allow you to append bytes to bytes to a NetStream.  As a result, I'm able to play an MPEG2 video in an Air video player by transcoding on the fly from MPEG2 to flv.  Currently, I encounter memory issues with large files but it does work with small files.

If your intention is simply to transcode and not play files then the memory issues I described likely wouldn't be an issue.  If I can help further, let me know.

With a little guidance from Bernd, I've been trying to build FFMPEG from Alchemy over the past month.  Here is the approach I'm taking in detail. 

Get FFMPEG building and debugging  with gcc  (/usr/bin/gcc). 

1. Create a CTD (C/C++) project in Eclipse.

2. Create a new makefile project

- Use Mac OS GCC toolchain

3. Install Lame

4. Run configure with the following options:

./configure --disable-shared --disable-vhook --disable-mmx --enable-debug --disable-ffserver

5. Build

7. Setup a debugging configuration to use ffmpeg_g

8. Set the debugger to gdb/mi

9. Set the GDB command set to "Standard (Mac OS)"

Experiment with configure to isolate the code related to the features you need.

1. Create a test that accomplishes what you want to with FFMPEG.  In my case, a subset of FFMPEG will accomplish what I need it to.

2. Note that if you need a specific component (demuxed, parser, decoder, etc…) you can disable all components and then enable specific components.  This example will enable only mpegvideo:

--disable-demuxers  --enable-demuxer=mpegvideo  

Try to build it with alchemy gcc and if (when) it fails, isolate the function that is failing with llc -debug.

1. When the debug fails it will leave behind build artifacts  (*.bc) files.  Find the bc file left behind.

2. Print the debug output to text file with a command that looks something like this:

llc -debug -march=avm2 -avm2-use-memuser -o=26006.achacks.as -avm2-package-name=cmodule.ffmpeg_g <build artifact file>.bc >& ~/Desktop/out.txt

Note: I think the exact arguments will differ from platform to platform.  To find the argument for your platform enable logging for gcc and check the gcc.log file.

Note: The output files will be quite large.  I've had one exceed 2GB. 

3. grep the log for "^===" to get a list of functions that compiled. 

cat out.txt | grep "^==="

The last function in the list is the function that caused the failure. 

4. Clean up that function.  This is the step that I can't give exact steps for.  Here are some general tricks I've used to get around this:

- As Bernd said look for wild casts.  In addition to what has already been said, I've fixed a few functions by eliminating the following casts:

(uint16_t*)

(const uint16_t*)

Note: While this fixed a few functions for me I don't think it would be correct to say all casts like this need to be eliminated.  I was in the middle of investigating these when I got diverted to other things.  At this point consider it something to look for and experiment with in a failing function.

- Another clue that may help is to look for warnings thrown by your compiler which can be seen in your IDE.

- I've also found that for my purposes some of the functions (specifically logging functions) can be eliminated entirely. 

- Any time I make and edit to the code I build and test it with Eclipse (/usr/bin/gcc) to ensure that the functionality I needed wasn't broken.

At this point I think I'm close but I haven't had time finish in the past few weeks.  If I finish it, I will post exactly what I did. 

I finally have a portion of FFMPEG compiling with Alchemy and running in a Flash App.  For a handful of reasons, I'm not going to dump my work to a zip file but, I will share everything I learned along the way.  In addition to what I mentioned earlier here are a few additional steps I would advise:

1. Use the latest version of FFMPEG. 

When I started using version 6.1 many of the earlier compile issues I had disappeared.  I didn't dig too deeply into why that was the case.  I suspect that much of the code Alchemy struggled with has been modified to Alchemy's liking. 

2. Disable Inline Assembly 

Be sure to include --disable-asm in your configure statement. 

3.  Math Function Improvisation

Some of the math functions were missing so I had to work around that.  One example, I replaced cbrtf  (Cube Root) references were replaced with pow(value, .333)

4. Allocate enough flash memory

Here's how you would set flash memory to 30MB:

ApplicationDomain.currentDomain.domainMemory.length = 31457280;

5. Glue Code

FFMPEG ultimately uses freed, fwrite, and seek to write contents to files and similar functions to write to streams.  I replaced these references to alchemy equivalents of AS3_ByteArray_readBytes, AS3_ByteArray_writeBytes, and AS3_ByteArray_seek.  Since function pointers were used in this section of the code, it was relatively non-intrusive to do.  The following was my basic approach when interacting with the FFMPEG with Flex/Flash.

- Read a file into a byte array

- Transcod the contents of the source byte array into a destination byte array.

- Play or save the destination byte array.

6. Ensure that compilation in C continues to work as you modify FFMPEG.

I used a small MakeFile change to switch back and forth between compiling for C and Alchemy. 

7. I recommend rewriting the MakeFile

I encountered issues compilation that I solved by building the library directly from the object files (Bypassing the static library phase).  Furthermore, I found the FFMPEG make files difficult to work with.  Here's excerpt from the file I wrote:

CC=gcc

CFLAGS=-DCOMPILE_FOR_ALCHEMY -DHAVE_AV_CONFIG_H -I. -std=c99 -mdynamic-no-pic -O3 -g -Wall

LIBAVCODEC_OBJS=libavcodec/aandcttab.o libavcodec/adpcm.o libavcodec/allcodecs.o ...

LIBAVDEVICE_OBJS=libavdevice/alldevices.o libavdevice/avdevice.o

LIBAVFORMAT_OBJS=libavformat/allformats.o libavformat/avc.o libavformat/avio.o …

LIBAVUTIL_OBJS=libavutil/adler32.o libavutil/aes.o libavutil/avstring.o …

LIBSWSCALE_OBJS=libswscale/options.o libswscale/rgb2rgb.o libswscale/swscale.o ..

FFMPEG_OBJS=ffmpeg.o

ARTIFACT=ffmpeg_g.swc

OBJS_LIGHT=ffmpeg.o libavformat/utils.o

all: ${LIBAVCODEC_OBJS} ${LIBAVDEVICE_OBJS} ${LIBAVFORMAT_OBJS} ${LIBAVUTIL_OBJS} ${LIBSWSCALE_OBJS} ${FFMPEG_OBJS}

@echo "starting the ffmpeg build ..."

${CC} ${LIBAVCODEC_OBJS} ${LIBAVDEVICE_OBJS} ${LIBAVFORMAT_OBJS} ${LIBAVUTIL_OBJS} ${LIBSWSCALE_OBJS} ${FFMPEG_OBJS} ${CFLAGS} -swc -o ${ARTIFACT}

@echo "finished the ffmpeg build"

libavcodec/*.o : libavcodec/*.c

@echo "compiling $< ..."

${CC} ${CFLAGS} -c $< -o $@

libavdevice/*.o : libavdevice/*.c

@echo "compiling $< ..."

${CC} ${CFLAGS} -c $< -o $@

libavformat/*.o : libavformat/*.c

@echo "compiling $< ..."

${CC} ${CFLAGS} -c $< -o $@

libavutil/*.o : libavutil/*.c

@echo "compiling $< ..."

${CC} ${CFLAGS} -c $< -o $@

libswscale/*.o : libswscale/*.c

@echo "compiling $< ..."

${CC} ${CFLAGS} -c $< -o $@

*.o : *.c

@echo "compiling $< ..."

${CC} ${CFLAGS} -c $< -o $@

I'm not finished yet.  I still have a few bugs to work through and hope to get pthreads working with it so that the app is not seized up while the transcode is taking place.  I hope this helps.  Let me know if you have any questions.  I'll do my best to respond in a timely manner.

That is correct.  The following command will read from stdin and write to stdout which can access with Native Processes in Air.  The ffmpeg command will look something like this:

ffmpeg -i - (other options) -

The "-i -" tells ffmpeg to read from stdin and the "-" at the end tells ffmpeg to write to stdout.  To test this with files do something like this:

ffmpeg -i - (other options) - < (path to input file) > (path to output file)

The Flex code will look something like this:

//declare the process

private var _process:NativeProcess = new NativeProcess();

//start the process

_process.start(nativeProcessCmdInfo);

//write to stdin

_process.standardInput.writeBytes(_buffer, 0, _buffer.length);

//read from stdout

_process.addEventListener(ProgressEvent.STANDARD_OUTPUT_DATA, writeToStream);

Let me know if this works for you.

Thanks,

Joe

That is an interesting idea...

I don't remember running into an error like that.  Can you tell me at a high level what your trying to do?  Feel free to send me an email directly.

Also, I forgot to mention earlier, you don't have to use LAME when compiling FFMPEG with Alchemy.  Atleast I didn't for the task I was trying to accomplish.