[FFmpeg-devel] [PATCH] floating-point input to libvorbis encoder

[Måns Rullgård]

Tomas H?rdin <tomas.hardin at codemill.se> writes:

> On Sat, 2010-09-18 at 12:12 -0400, Justin Ruggles wrote:
>> Hi,
>> 
>> libvorbis takes floating-point samples as input.  Our libvorbis wrapper
>> currently only accepts 16-bit input and converts it to float.  It seems
>> better to me to have it only accept float input and leave the conversion
>> outside of the encoder.
>> 
>> -Justin
>> 
>> plain text document attachment (libvorbis_float_input.patch)
>> Index: libavcodec/libvorbis.c
>> ===================================================================
>> --- libavcodec/libvorbis.c	(revision 25138)
>> +++ libavcodec/libvorbis.c	(working copy)
>> @@ -145,7 +145,7 @@
>>  {
>>      OggVorbisContext *context = avccontext->priv_data ;
>>      ogg_packet op ;
>> -    signed short *audio = data ;
>> +    float *audio = data;
>>      int l;
>>  
>>      if(data) {
>> @@ -158,7 +158,7 @@
>>              int co = (channels > 8) ? c :
>>                  ff_vorbis_encoding_channel_layout_offsets[channels-1][c];
>>              for(l = 0 ; l < samples ; l++)
>> -                buffer[c][l]=audio[l*channels+co]/32768.f;
>> +                buffer[c][l] = audio[l*channels+co];
>>          }
>>          vorbis_analysis_wrote(&context->vd, samples) ;
>>      } else {
>> @@ -238,6 +238,6 @@
>>      oggvorbis_encode_frame,
>>      oggvorbis_encode_close,
>>      .capabilities= CODEC_CAP_DELAY,
>> -    .sample_fmts = (const enum SampleFormat[]){SAMPLE_FMT_S16,SAMPLE_FMT_NONE},
>> +    .sample_fmts = (const enum SampleFormat[]){SAMPLE_FMT_FLT,SAMPLE_FMT_NONE},
>>      .long_name= NULL_IF_CONFIG_SMALL("libvorbis Vorbis"),
>>  } ;
>
> Please correct me if I'm wrong, but doesn't this require a major version
> bump?

Strictly speaking, no.  The codec exports the list of supported input
formats, and a proper app should perform any conversions necessary.
That said, there are probably many apps assuming s16 is supported, and
they would indeed be broken by this change.  Do we care about those?

> Also, is there no way to feed libvorbis the input buffer directly?

Only if the layouts are the same, which seems not to be the case.

-- 
M?ns Rullg?rd
mans at mansr.com