Messages in this thread | | | Subject | Re: [PATCH 10/11] ASoC: qdsp6-dai: add gapless support | From | Pierre-Louis Bossart <> | Date | Wed, 8 Jul 2020 11:58:21 -0500 |
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>> right, but the key point is 'switch between streams'. That means a >> more complex/capable implementation that should be advertised as such >> to applications. This is not the default behavior assumed initially: >> to allow for minimal implementations in memory-constrained devices, we >> assumed gapless was supported with a single decoder. >> >> Maybe the right way to do this is extend the snd_compr_caps structure: >> >> /** >> * struct snd_compr_caps - caps descriptor >> * @codecs: pointer to array of codecs >> * @direction: direction supported. Of type snd_compr_direction >> * @min_fragment_size: minimum fragment supported by DSP >> * @max_fragment_size: maximum fragment supported by DSP >> * @min_fragments: min fragments supported by DSP >> * @max_fragments: max fragments supported by DSP >> * @num_codecs: number of codecs supported >> * @reserved: reserved field >> */ >> struct snd_compr_caps { >> __u32 num_codecs; >> __u32 direction; >> __u32 min_fragment_size; >> __u32 max_fragment_size; >> __u32 min_fragments; >> __u32 max_fragments; >> __u32 codecs[MAX_NUM_CODECS]; >> __u32 reserved[11]; >> } __attribute__((packed, aligned(4))); >> >> >> and use a reserved field to provide info on capabilities, and filter >> the set_codec_params() addition based this capability - i.e. return >> -ENOTSUP in 'traditional' implementations based on a single >> 'stream'/decoder instance.
I think this is also what Mark was referring to earlier.
> Sounds good! > I will give it a go and see how it ends up!
Glad to see this discussion progressing.
We may also want to document the 3 possible ways of supporting gapless playback while we are at it: a) with the existing single decoder assumption b) with your suggested solution with a switch at the DSP level c) with 2 streams at the userspace level and a switch/x-fade at the DSP level - which may simplify userspace quite a bit and was the initial design in a non-Linux OS.
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