Hi,
On 13.03.2015 22:46, Christophe Gisquet wrote:
> 2015-03-13 22:28 GMT+01:00 Andreas Cadhalpun
> <andreas.cadhal...@googlemail.com>:
>> -int ff_eac3_parse_header(AC3DecodeContext *s);
>> +static int ff_eac3_parse_header(AC3DecodeContext *s);
>
> It's somewhat cosmetics, but if these functions become static, they
> would better drop the ff_ prefix.
I don't mind the names, but I tried to keep the changes minimal, to
ease backporting the fix.
The names can be changed in a follow-up patch.
>> - float accum = 0.0f;
>> + INTFLOAT accum = 0.0f;
> [...]
>> for (i = 0; i < bandsize; i++) {
>> - float coeff = s->transform_coeffs[ch][bin++];
>> + INTFLOAT coeff = s->transform_coeffs[ch][bin++];
>> accum += coeff * coeff;
> [...]
>> - float nscale = s->spx_noise_blend[ch][bnd] * rms_energy[bnd] *
>> (1.0f / INT32_MIN);
>> - float sscale = s->spx_signal_blend[ch][bnd];
>> + INTFLOAT nscale = s->spx_noise_blend[ch][bnd] * rms_energy[bnd]
>> * (1.0f / INT32_MIN);
>> + INTFLOAT sscale = s->spx_signal_blend[ch][bnd];
>> for (i = 0; i < s->spx_band_sizes[bnd]; i++) {
>> - float noise = nscale * (int32_t)av_lfg_get(&s->dith_state);
>> + INTFLOAT noise = nscale *
>> (int32_t)av_lfg_get(&s->dith_state);
>
> Does that work at all? I mean, if it's fixedpoint, I would have
> expected some renormalization, various things to avoid overflows,
> potential warnings because of casts, etc.
>
> And is the output on eac3 samples, eg here:
> http://samples.mplayerhq.hu/A-codecs/AC3/eac3/
> (particularly the spx ones)
> anything listenable?
>
> Maybe the extensions should simply be declared as unsupported by the fp
> version?
It works well enough, I think.
Without this patch:
$ ffmpeg -c:a ac3_fixed -i ./rio_bravo_mono_64_spx.ac3 broken.ac3
[eac3 @ 0x2401560] Estimating duration from bitrate, this may be inaccurate
Input #0, eac3, from '/tmp/rio_bravo_mono_64_spx.ac3':
Duration: 00:04:22.18, start: 0.000000, bitrate: 64 kb/s
Stream #0:0: Audio: ac3, 48000 Hz, mono, s16p, 64 kb/s
Output #0, ac3, to '/tmp/broken.ac3':
Metadata:
encoder : Lavf56.25.101
Stream #0:0: Audio: ac3, 48000 Hz, mono, fltp, 96 kb/s
Metadata:
encoder : Lavc56.26.100 ac3
Stream mapping:
Stream #0:0 -> #0:0 (ac3 (ac3_fixed) -> ac3 (native))
Press [q] to stop, [?] for help
[ac3_fixed @ 0x24024c0] exponent out-of-range
[ac3_fixed @ 0x24024c0] error decoding the audio block
...
many more such errors
...
[ac3_fixed @ 0x24024c0] exponent out-of-range
[ac3_fixed @ 0x24024c0] error decoding the audio block
Segmentation fault (core dumped)
Make sure the volume is at a low level, when playing the
broken.ac3, or your ears will hurt.
With this patch:
$ ffmpeg -c:a ac3_fixed -i ./rio_bravo_mono_64_spx.ac3 out.ac3
[eac3 @ 0xb5b560] Estimating duration from bitrate, this may be inaccurate
Input #0, eac3, from '/tmp/rio_bravo_mono_64_spx.ac3':
Duration: 00:04:22.18, start: 0.000000, bitrate: 64 kb/s
Stream #0:0: Audio: ac3, 48000 Hz, mono, s16p, 64 kb/s
Output #0, ac3, to '/tmp/out.ac3':
Metadata:
encoder : Lavf56.25.101
Stream #0:0: Audio: ac3, 48000 Hz, mono, fltp, 96 kb/s
Metadata:
encoder : Lavc56.26.100 ac3
Stream mapping:
Stream #0:0 -> #0:0 (ac3 (ac3_fixed) -> ac3 (native))
Press [q] to stop, [?] for help
size= 3072kB time=00:04:22.17 bitrate= 96.0kbits/s
video:0kB audio:3072kB subtitle:0kB other streams:0kB global headers:0kB muxing
overhead: 0.000000%
The out.ac3 sounds much like the input.
Best regards,
Andreas
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