Deprecated functions in ffmpeg library

Well, I have some code that uses some old FFMPEG library, and now, as I updated my laptop to Fedora 18, it turns out that those functions are gone for good. I found some resources about how to port old code (here, here and here), but since it wasn't what I needed I decided to write my own version. So, here we go.

url_open()

This function has been changed to avio_open. There is also url_close which is renamed to avio_close. This information I found here.

av_new_stream()

This function is still supported as of FFMPEG 1.0.1 but it is marked as deprecated. It will be replaced with avformat_new_stream(). Suppose that the old code was:

AVStream *st = av_new_stream(oc, i);

the modified code should be:

AVStream *st = avformat_new_stream(oc, NULL);
st->id = i

Be careful to check first that st isn't NULL!

dump_format()

This function was renamed to av_dump_format().

av_write_header()

Replaced with avformat_write_header() that accepts two arguments instead of one. Pass NULL as the second argument to get identical behavior to the old function.

av_codec_open()

This one is replaced with av_codec_open2(). The replacement function accepts three arguments instead of two, but put NULL as a third argument to get the same behavior as the old function.

avcodec_encode_audio()

Replaced with avcodec_encode_audio2().

av_set_parameters()

I couldn't fine the replacement for this one. First, I've found that this function doesn't have replacement. But it was when it was still available in FFMPEG, even though deprecated. Then, they removed it, and thus it has to have replacement. In certain places I found that they only disabled it, on others that its parameters have to be passed  to avformat_write_header. In the end, I gave up because I didn't need working version of that part of the code for now. Since in my case avformat_alloc_context() is called and then av_set_parameters(), last what I looked at was to call avformat_alloc_output_context2() instead of avformat_alloc_context(). But the change is not trivial so I skipped it.

SampleFormat

This enum has been renamed AVSampleFormat.

URL_WRONLY 

This constant has been replaced with AVIO_FLAG_WRITE.

SAMPLE_FMT_U8, SAMPLE_FMT_S16, SAMPLE_FMT_S32, etc.

Those are prefixed now with AV_, so use AV_SAMPLE_FMT_U8, AV_SAMPLE_FMT_S16, etc.

Problem with avformat_open_input()

I lost too much time because of a misleading error message reported by avformat_open_input function! I used the following code that exhibit the error:

AVFormatContext *pFormatCtx = NULL;
...
ret = avformat_open_input(&pFormatCtx, argv[1], NULL, NULL);
if (ret < 0)
   print_error_and_exit(ret, "avformat_open_input()");

print_error_and_exit() is a helper function that uses av_strerror() to give textual representation of the error code stored in ret. Running this code produced the following output:

$ ./a.out infile.wav outfile.wav
avformat_open_input(): No such file or directory

But the infile.wav was there! Using strace I found that open system call wasn't called and so it was certainly an internal error. This was frustrating! The reason I started to write this code was to find out why I'm getting another error in VoIP tool simulator, but I was stuck on something even more basic: Not being able to open a wav file. Googling around I finally found the following link which explained me a real cause of the error, i.e. I forgot to call av_register_all() initialization function.

This again shows how important good error reporting is, in both libraries and application programs!

I had also another problem with the previous code. It was segfaulting within avformat_open_input(). At first, I thought that I found a bug within a library but then I realized I forgot to initialize pFormatCtx to NULL. Namely, allocating a dynamic variable on stack didn't zero it so it was non-NULL and avformat_open_input() misbehaved. Mea culpa! :)