what does it means " filter(s) 'a52 '->'f32l' "

[annie0716]

Dear all friends
I am a beginner for VLC, hope any friend can help me on DD/DTS issue.
I am preparing patch for a HDMI CODEC, and I am confused by the definition of "HDA_PCM_TYPE_HDMI" and "HDA_PCM_TYPE_SPDIF".
Now I want to confirm if our coded can support DD/DTS. If I set the pcm_type as HDA_PCM_TYPE_HDMI, and try to play a song with ac3 format by VLC player. My HD TV can play the sound with Audio Channels set as "Dolby Surround" and the Audio Device set as "Stereo"; but when I set the Audio Device as "A/52 over S/PDIF", no sound can be outputted.
If I set the pcm_type as HDA_PCM_TYPE_SPDIF, although no Audio Deive can be selected, but there is sound outputted when Audio Channel is set as "Dolby Surround". But by tracing the debug info outputted by vlc, it seams that the AC3 is converted by pulse module in both cases, so I think maybe the dolby is converted to stereo. I don't know if I am right.

The debug info I got are :
1, If I declared codec as HDA_PCM_TYPE_SPDIF"(no "Audio Device" can be selected), no matter "Audio Channels" are selected as "Dolby" or "Reverse Stereo", it seams that the audio streams is converted to f32l;
If I declared codec as HDA_PCM_TYPE_HDMI"("Audio Device" can be selected, set as "Stereo"), , no matter "Audio Channels" are selected as "Dolby" or "Reverse Stereo", ", it seams that the audio streams is converted to f32l;
filter(s) 'a52 '->'f32l' "

2, If I declared codec as HDA_PCM_TYPE_HDMI"("Audio Device" can be selected, set as "A/52 over S/PDIF"), , no matter "Audio Channels" are selected as "Dolby" or "Reverse Stereo", ", it seams that the audio streams is converted to 'spdi';

[0xa0ff8d4] main audio output debug: filter(s) 'a52 '->'spdi' 48000 Hz->48000 Hz Dolby->Dolby
[0xa10a6dc] main audio filter debug: looking for audio filter module: 14 candidates
[0xa10a6dc] main audio filter debug: using audio filter module "a52tospdif"

I wonder what it seams for "filter(s) 'a52 '->'f32l'" and "filter(s) 'a52 '->'spdi' ", what is difference for audio codec?

Thanks a lot.
BR//Annie

[Rémi Denis-Courmont]

a52->f32l means converting A/52 to little-endian single precision, in other words decoding. a52->spdi means converting from A/52 to S/PDIF, in other words encapsulating AC-3 into S/PDIF frames.

Which one is used depends on what the audio output plugin requested as output format.

[annie0716]

Thanks so much!