[linuxtv-softmpeg] Re: audio.c patch

[Michael Hunold <hunold@convergence.de>]

Hello Carsten,

thanks for your work!

On 02/24/04 20:38, ckroll@arcor.de wrote:
> I finally figured out what the problem with my audio stream playback was.
> I try to play an SVCD compliant mpeg stream. The audio has a 44100Hz sample 
> rate. With this sample rate the frame size is not constant.
Hm, this sounds bogus. MP2 audio has always a fixed frame size (have a 
look at mpegaudio.c)

Are you sure your SVCD contains MP2 audio?

Can you upload a few megabytes of that stream to anywhere, so I can have 
a look?

> That caused lots 
> of problems. I fixed this issue in audio.c.
> Unfortunately I do not know how it affects other types of mpeg streams. In 
> theory it should be fine :-).
> So I attach a patch that contains my fix. Please review it in case I made any 
> mistakes here. The audio decoding now works for this, but the playback is 
> still jerky.
Most likely it will have side effects. Did you try if "dfb_ts" still works?

>  	if (d->as.len >= ac.frame_size) {
>  		int ret;
> -		int i = 0;
>  		unsigned char *ptr = d->as.buf;
>  		while (d->as.len > ac.frame_size) {
>  			int chunk_len = 0;
> -			AUDIO_PES("writing %d bytes to avcodec\n", ac.frame_size);
> -			ret = avcodec_decode_audio(d->codec_ctx, (int16_t *) 
(d->current->buf + d->current->len), &chunk_len, ptr, ac.frame_size);
> -			if (ac.frame_size == ret) {
> +			AUDIO_PES("writing %d bytes to avcodec\n", d->as.len);
> +			ret = avcodec_decode_audio(d->codec_ctx, (int16_t *) 
(d->current->buf + d->current->len), &chunk_len, ptr, d->as.len);

This looks bogus. The check d->as.len >= ac.frame_size doesn't make any 
sense anymore, when you later write out the whole d->as.len bytes 
because you think the frame size is not constant. Against what frame 
size does this "check" compare?

> I will look at the video decoding problem next. I guess it has to do with the 
> frame resolution not being 768x576.
Make sure your refresh rate is 50Hz. "fbset" will tell you that:

hunoldwin root # fbset

mode "720x576-50"
    # D: 32.043 MHz, H: 31.049 kHz, V: 49.999 Hz
                                      ^^^^^^^^^^^

> regards Carsten
CU
Michael.


--
Info:  To unsubscribe send a mail to ecartis@linuxtv.org with 
"unsubscribe linuxtv-softmpeg" as subject.