[alsa-devel] [PATCH v2] Fix forward/rewind support in iec958 plugin

[Raymond Yau]

>
> When forwarding or rewinding, the frame counter was not updated. This
> could result in corrupted channel status words or misplaced Z-type
> preamble.

Do you mean it is the responsibility for a52 and dca plugin to return the
SAFE value returned by snd_pcm_rewindable and snd_pcm_forwardable since
they enocde the audio and padding zeros and write to IEC958 ?

>
> +static snd_pcm_sframes_t snd_pcm_iec958_rewind(snd_pcm_t *pcm,
snd_pcm_uframes_t frames)
> +{
> +       unsigned int counter_decrement;
> +       snd_pcm_iec958_t *iec = pcm->private_data;
> +       snd_pcm_sframes_t result = snd_pcm_plugin_rewind(pcm, frames);
> +       if (result <= 0)
> +               return result;
> +
> +       counter_decrement = result % 192;
> +       iec->counter += 192 - counter_decrement;
> +       iec->counter %= 192;
> +       return result;
> +}
> +
> +static snd_pcm_sframes_t snd_pcm_iec958_forward(snd_pcm_t *pcm,
snd_pcm_uframes_t frames)
> +
> +{
> +       unsigned int counter_increment;
> +       snd_pcm_iec958_t *iec = pcm->private_data;
> +       snd_pcm_sframes_t result = snd_pcm_plugin_rewind(pcm, frames);
> +       if (result <= 0)
> +               return result;
> +
> +       counter_increment = result % 192;
> +       iec->counter += counter_increment;
> +       iec->counter %= 192;
> +       return result;
> +}
> +