[mythtv] [mythtv-commits] Ticket #5900: AO: Generalise upmix and AC-3 encoding
John P Poet
jppoet at gmail.com
Mon Nov 10 19:45:30 UTC 2008
On Mon, Nov 10, 2008 at 12:24 PM, foo bar <foobum at gmail.com> wrote:
>> Modern ALSA will automatically resample to 48, but only for cards
>> that need it. Mine does not.
> Modern ALSA does software mixing by default and resamples to 48k
> before doing so.
> That the card supports the original sample rate makes no difference.
>> How are you defining SNR? There is no way you can resample a
>> 44.1KHz source into 48KHz and have it be "accurate".
> I would venture that it's inaudibly inaccurate.
> Details of the resampler, including SNR definition, here:
> We use SRC_SINC_BEST_QUALITY.
>> Yeah, I just mean *that* feature of the patch. It would be nice if
>> foo could identify which part of the patch I would need to revert.
>> The rest of it could be useful.
> Assuming your card/receiver can do both 44.1k AC-3 and PCM, the
> following should do what you want:
> --- libs/libmyth/audiooutputbase.cpp 2008-11-10 19:08:28.000000000 +0000
> +++ libs/libmyth/audiooutputbase.cpp 2008-11-10 19:09:41.000000000 +0000
> @@ -252,7 +252,7 @@
> VERBOSE(VB_AUDIO, LOC + "Creating AC-3 Encoder");
> encoder = new AudioOutputDigitalEncoder();
> - if (!encoder->Init(CODEC_ID_AC3, 448000, 48000,
> + if (!encoder->Init(CODEC_ID_AC3, 448000, audio_samplerate,
> configured_audio_channels, audio_reenc))
> VERBOSE(VB_AUDIO, LOC + "Can't create AC-3 encoder");
> @@ -272,7 +272,7 @@
> // Always resample to 48k - many cards can't do anything else
> // and ALSA will do it with linear interpolation (yuk) if we don't anyway
> - if (audio_samplerate != 48000)
> + if (0)
> int error;
> audio_samplerate = 48000;
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
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