[FFmpeg-devel] [PATCH 1/3] Add replay_gain and find_peak_sample options to libmp3lame

[Michael Niedermayer]

On Fri, May 23, 2014 at 07:40:14PM -0700, Giovanni Motta wrote:
> Add Lame tag to the Xing/Info header of mp3 files.
> 
> Fixes ticket #3577
> 
> A few notes/comments:
> 
> - A failing FATE test has been updated with new CRC.
> 
> - The Lame info tag is generated by libmp3lame and passed to the mp3enc via extradata.
> 
> - To keep the size of the tag constant and simplify the code, vbr_scale is always added.
> 
> - The Lame string vendor in the tag is fixed length, so vendor is trimmed
>   to 9 bytes and padded with 0x20 if shorter.
> 
> - replay_gain and find_peak need a version of lame patched with
>   libmp3lame/lame.c Revision 1.367 (patch tracker item #66): http://sourceforge.net/p/lame/patches/66/
>   They have no effect otherwise.
> 

> - find_peak_sample only works if Lame is configured with --enable-decoder.
>   It has no effect otherwise.

there should be an error or warning printed if the user specifies an
option that doesnt work with the used Lame


> 
> - Some fields in the Lame tag are not set because not accessible from
>   the set/get API (preset and noise shaping, for example). I will bring this to
>   the attention of the Lame developers and help there with any change if we
>   decide to merge the patch.
> 
> Thanks
> 
> Giovanni
> 
> 
> 
> ---
>  libavcodec/libmp3lame.c | 17 +++++++++++++----
>  1 file changed, 13 insertions(+), 4 deletions(-)
> 
> diff --git a/libavcodec/libmp3lame.c b/libavcodec/libmp3lame.c
> index a8c39cc..01b8c7b 100644
> --- a/libavcodec/libmp3lame.c
> +++ b/libavcodec/libmp3lame.c
> @@ -48,6 +48,8 @@ typedef struct LAMEContext {
>      int buffer_index;
>      int buffer_size;
>      int reservoir;
> +    int find_peak_sample;
> +    int replay_gain;
>      int joint_stereo;
>      int abr;
>      float *samples_flt[2];
> @@ -97,7 +99,6 @@ static av_cold int mp3lame_encode_init(AVCodecContext *avctx)
>      if ((s->gfp = lame_init()) == NULL)
>          return AVERROR(ENOMEM);
> 
> -
>      lame_set_num_channels(s->gfp, avctx->channels);
>      lame_set_mode(s->gfp, avctx->channels > 1 ? s->joint_stereo ? JOINT_STEREO : STEREO : MONO);
> 
> @@ -131,6 +132,12 @@ static av_cold int mp3lame_encode_init(AVCodecContext *avctx)
>      /* bit reservoir usage */
>      lame_set_disable_reservoir(s->gfp, !s->reservoir);
> 
> +    /* find peak sample */
> +    lame_set_decode_on_the_fly(s->gfp, s->find_peak_sample);
> +
> +    /* compute replay gain */
> +    lame_set_findReplayGain(s->gfp, s->replay_gain);
> +
>      /* set specified parameters */
>      if (lame_init_params(s->gfp) < 0) {
>          ret = -1;
> @@ -267,9 +274,11 @@ static int mp3lame_encode_frame(AVCodecContext *avctx, AVPacket *avpkt,
>  #define OFFSET(x) offsetof(LAMEContext, x)
>  #define AE AV_OPT_FLAG_AUDIO_PARAM | AV_OPT_FLAG_ENCODING_PARAM
>  static const AVOption options[] = {
> -    { "reservoir",    "use bit reservoir", OFFSET(reservoir),    AV_OPT_TYPE_INT, { .i64 = 1 }, 0, 1, AE },
> -    { "joint_stereo", "use joint stereo",  OFFSET(joint_stereo), AV_OPT_TYPE_INT, { .i64 = 1 }, 0, 1, AE },
> -    { "abr",          "use ABR",           OFFSET(abr),          AV_OPT_TYPE_INT, { .i64 = 0 }, 0, 1, AE },
> +    { "reservoir",        "use bit reservoir",   OFFSET(reservoir),        AV_OPT_TYPE_INT, { .i64 = 1 }, 0, 1, AE },
> +    { "find_peak_sample", "find peak sample",    OFFSET(find_peak_sample), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, 1, AE },
> +    { "replay_gain",      "compute replay gain", OFFSET(replay_gain),      AV_OPT_TYPE_INT, { .i64 = 0 }, 0, 1, AE },
> +    { "joint_stereo",     "use joint stereo",    OFFSET(joint_stereo),     AV_OPT_TYPE_INT, { .i64 = 1 }, 0, 1, AE },
> +    { "abr",              "use ABR",             OFFSET(abr),              AV_OPT_TYPE_INT, { .i64 = 0 }, 0, 1, AE },
>      { NULL },

missing documentation (in doc/...)

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Asymptotically faster algorithms should always be preferred if you have
asymptotical amounts of data
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