[FFmpeg-devel] [PATCH 1/1] avcodec/pcm: reduce code size
Andreas Rheinhardt
andreas.rheinhardt at outlook.com
Mon May 19 16:03:10 EEST 2025
chenyu202107 at gmail.com:
> From: chenyu <chenyu202107 at gmail.com>
>
> add depends to pcm.c for reducing size when ALAW/MULAW/VIDC not defined
>
> Signed-off-by: chenyu <chenyu202107 at gmail.com>
> ---
> libavcodec/pcm.c | 36 +++++++++++++++++++++++++++++++-----
> libavcodec/pcm_tablegen.h | 22 ++++++++++++++++++++++
> 2 files changed, 53 insertions(+), 5 deletions(-)
>
> diff --git a/libavcodec/pcm.c b/libavcodec/pcm.c
> index bff61f2195..60a2c544a8 100644
> --- a/libavcodec/pcm.c
> +++ b/libavcodec/pcm.c
> @@ -44,15 +44,20 @@ static av_cold int pcm_encode_init(AVCodecContext *avctx)
> #if !CONFIG_HARDCODED_TABLES
> switch (avctx->codec->id) {
> #define INIT_ONCE(id, name) \
> - case AV_CODEC_ID_PCM_ ## id: \
> - if (CONFIG_PCM_ ## id ## _ENCODER) { \
> + case AV_CODEC_ID_PCM_ ## id: { \
> static AVOnce init_static_once = AV_ONCE_INIT; \
> ff_thread_once(&init_static_once, pcm_ ## name ## _tableinit); \
> - } \
> - break
> + break; \
> + }
> +#if CONFIG_PCM_ALAW_DECODER || CONFIG_PCM_ALAW_ENCODER
> INIT_ONCE(ALAW, alaw);
> +#endif
> +#if CONFIG_PCM_MULAW_DECODER || CONFIG_PCM_MULAW_ENCODER
> INIT_ONCE(MULAW, ulaw);
> +#endif
> +#if CONFIG_PCM_VIDC_DECODER || CONFIG_PCM_VIDC_ENCODER
> INIT_ONCE(VIDC, vidc);
> +#endif
The macro already checks whether the relevant encoder is enabled; your
code meanwhile enables the code when the encoder or the decoder is
enabled, although only the encoders will ever use this.
> default:
> break;
> }
> @@ -216,24 +221,30 @@ static int pcm_encode_frame(AVCodecContext *avctx, AVPacket *avpkt,
> bytestream_put_buffer(&dst, src, n * sample_size);
> }
> break;
> +#if CONFIG_PCM_ALAW_DECODER || CONFIG_PCM_ALAW_ENCODER
> case AV_CODEC_ID_PCM_ALAW:
> for (; n > 0; n--) {
> v = *samples++;
> *dst++ = linear_to_alaw[(v + 32768) >> 2];
> }
> break;
> +#endif
> +#if CONFIG_PCM_MULAW_DECODER || CONFIG_PCM_MULAW_ENCODER
> case AV_CODEC_ID_PCM_MULAW:
> for (; n > 0; n--) {
> v = *samples++;
> *dst++ = linear_to_ulaw[(v + 32768) >> 2];
> }
> break;
> +#endif
> +#if CONFIG_PCM_VIDC_DECODER || CONFIG_PCM_VIDC_ENCODER
> case AV_CODEC_ID_PCM_VIDC:
> for (; n > 0; n--) {
> v = *samples++;
> *dst++ = linear_to_vidc[(v + 32768) >> 2];
> }
> break;
> +#endif
> default:
> return -1;
> }
> @@ -327,20 +338,25 @@ static av_cold av_unused int pcm_lut_decode_init(AVCodecContext *avctx)
> PCMLUTDecode *s = avctx->priv_data;
>
> switch (avctx->codec_id) {
> +#if CONFIG_PCM_ALAW_DECODER || CONFIG_PCM_ALAW_ENCODER
> case AV_CODEC_ID_PCM_ALAW:
> for (int i = 0; i < 256; i++)
> s->table[i] = alaw2linear(i);
> break;
> +#endif
> +#if CONFIG_PCM_MULAW_DECODER || CONFIG_PCM_MULAW_ENCODER
> case AV_CODEC_ID_PCM_MULAW:
> for (int i = 0; i < 256; i++)
> s->table[i] = ulaw2linear(i);
> break;
> +#endif
> +#if CONFIG_PCM_VIDC_DECODER || CONFIG_PCM_VIDC_ENCODER
> case AV_CODEC_ID_PCM_VIDC:
> for (int i = 0; i < 256; i++)
> s->table[i] = vidc2linear(i);
> break;
> }
> -
> +#endif
The encoder checks here are wrong; and the placement of the last endif
is wrong, too.
> avctx->sample_fmt = AV_SAMPLE_FMT_S16;
> s->base.sample_size = 1;
>
> @@ -545,6 +561,9 @@ static int pcm_decode_frame(AVCodecContext *avctx, AVFrame *frame,
> bytestream_get_buffer(&src, samples, n * sample_size);
> }
> break;
> +#if CONFIG_PCM_ALAW_DECODER || CONFIG_PCM_ALAW_ENCODER || \
> + CONFIG_PCM_MULAW_DECODER || CONFIG_PCM_MULAW_ENCODER || \
> + CONFIG_PCM_VIDC_DECODER || CONFIG_PCM_VIDC_ENCODER
This should not check for the encoders at all, because this is in the
decoder.
> case AV_CODEC_ID_PCM_ALAW:
> case AV_CODEC_ID_PCM_MULAW:
> case AV_CODEC_ID_PCM_VIDC: {
> @@ -555,6 +574,7 @@ static int pcm_decode_frame(AVCodecContext *avctx, AVFrame *frame,
> *samples_16++ = lut[*src++];
> break;
> }
> +#endif
> case AV_CODEC_ID_PCM_LXF:
> {
> int i;
> @@ -655,7 +675,9 @@ const FFCodec ff_ ## name_ ## _decoder = { \
> * to the table in pcm_decode_init() as well. */
> // AV_CODEC_ID_* pcm_* name
> // AV_SAMPLE_FMT_* long name DecodeContext decode init func
> +#if CONFIG_PCM_ALAW_DECODER || CONFIG_PCM_ALAW_ENCODER
> PCM_CODEC_EXT(ALAW, S16, alaw, "PCM A-law / G.711 A-law", PCMLUTDecode, pcm_lut_decode_init);
> +#endif
These macros already contain implicit checks to ensure that only the
FFCodecs for actually enabled codecs are included in the binary.
> PCM_DEC_EXT (F16LE, FLT, f16le, "PCM 16.8 floating point little-endian", PCMScaleDecode, pcm_scale_decode_init);
> PCM_DEC_EXT (F24LE, FLT, f24le, "PCM 24.0 floating point little-endian", PCMScaleDecode, pcm_scale_decode_init);
> PCM_CODEC (F32BE, FLT, f32be, "PCM 32-bit floating point big-endian");
> @@ -663,7 +685,9 @@ PCM_CODEC (F32LE, FLT, f32le, "PCM 32-bit floating point little
> PCM_CODEC (F64BE, DBL, f64be, "PCM 64-bit floating point big-endian");
> PCM_CODEC (F64LE, DBL, f64le, "PCM 64-bit floating point little-endian");
> PCM_DECODER (LXF, S32P,lxf, "PCM signed 20-bit little-endian planar");
> +#if CONFIG_PCM_MULAW_DECODER || CONFIG_PCM_MULAW_ENCODER
> PCM_CODEC_EXT(MULAW, S16, mulaw, "PCM mu-law / G.711 mu-law", PCMLUTDecode, pcm_lut_decode_init);
> +#endif
> PCM_CODEC (S8, U8, s8, "PCM signed 8-bit");
> PCM_CODEC (S8_PLANAR, U8P, s8_planar, "PCM signed 8-bit planar");
> PCM_CODEC (S16BE, S16, s16be, "PCM signed 16-bit big-endian");
> @@ -686,5 +710,7 @@ PCM_CODEC (U32BE, S32, u32be, "PCM unsigned 32-bit big-endian")
> PCM_CODEC (U32LE, S32, u32le, "PCM unsigned 32-bit little-endian");
> PCM_CODEC (S64BE, S64, s64be, "PCM signed 64-bit big-endian");
> PCM_CODEC (S64LE, S64, s64le, "PCM signed 64-bit little-endian");
> +#if CONFIG_PCM_VIDC_DECODER || CONFIG_PCM_VIDC_ENCODER
> PCM_CODEC_EXT(VIDC, S16, vidc, "PCM Archimedes VIDC", PCMLUTDecode, pcm_lut_decode_init);
> +#endif
> PCM_DECODER (SGA, U8, sga, "PCM SGA");
> diff --git a/libavcodec/pcm_tablegen.h b/libavcodec/pcm_tablegen.h
> index 7274c3cd17..590ba59814 100644
> --- a/libavcodec/pcm_tablegen.h
> +++ b/libavcodec/pcm_tablegen.h
> @@ -42,6 +42,7 @@
> #define VIDC_SEG_SHIFT (5)
> #define VIDC_SEG_MASK (0xE0)
>
> +#if CONFIG_PCM_ALAW_DECODER || CONFIG_PCM_ALAW_ENCODER
> /* alaw2linear() - Convert an A-law value to 16-bit linear PCM */
> static av_cold int alaw2linear(unsigned char a_val)
> {
> @@ -57,7 +58,9 @@ static av_cold int alaw2linear(unsigned char a_val)
>
> return (a_val & SIGN_BIT) ? t : -t;
> }
> +#endif
>
> +#if CONFIG_PCM_MULAW_DECODER || CONFIG_PCM_MULAW_ENCODER
> static av_cold int ulaw2linear(unsigned char u_val)
> {
> int t;
> @@ -74,7 +77,9 @@ static av_cold int ulaw2linear(unsigned char u_val)
>
> return (u_val & SIGN_BIT) ? (BIAS - t) : (t - BIAS);
> }
> +#endif
>
> +#if CONFIG_PCM_VIDC_DECODER || CONFIG_PCM_VIDC_ENCODER
> static av_cold int vidc2linear(unsigned char u_val)
> {
> int t;
> @@ -88,6 +93,7 @@ static av_cold int vidc2linear(unsigned char u_val)
>
> return (u_val & VIDC_SIGN_BIT) ? (BIAS - t) : (t - BIAS);
> }
> +#endif
>
> #if CONFIG_HARDCODED_TABLES
> #define pcm_alaw_tableinit()
> @@ -96,10 +102,19 @@ static av_cold int vidc2linear(unsigned char u_val)
> #include "libavcodec/pcm_tables.h"
> #else
> /* 16384 entries per table */
> +#if CONFIG_PCM_ALAW_DECODER || CONFIG_PCM_ALAW_ENCODER
> static uint8_t linear_to_alaw[16384];
> +#endif
> +#if CONFIG_PCM_MULAW_DECODER || CONFIG_PCM_MULAW_ENCODER
> static uint8_t linear_to_ulaw[16384];
> +#endif
> +#if CONFIG_PCM_VIDC_DECODER || CONFIG_PCM_VIDC_ENCODER
> static uint8_t linear_to_vidc[16384];
> +#endif
>
> +#if CONFIG_PCM_ALAW_DECODER || CONFIG_PCM_ALAW_ENCODER || \
> + CONFIG_PCM_MULAW_DECODER || CONFIG_PCM_MULAW_ENCODER || \
> + CONFIG_PCM_VIDC_DECODER || CONFIG_PCM_VIDC_ENCODER
> static av_cold void build_xlaw_table(uint8_t *linear_to_xlaw,
> int (*xlaw2linear)(unsigned char),
> int mask)
> @@ -123,21 +138,28 @@ static av_cold void build_xlaw_table(uint8_t *linear_to_xlaw,
> }
> linear_to_xlaw[0] = linear_to_xlaw[1];
> }
> +#endif
>
> +#if CONFIG_PCM_ALAW_DECODER || CONFIG_PCM_ALAW_ENCODER
> static void pcm_alaw_tableinit(void)
> {
> build_xlaw_table(linear_to_alaw, alaw2linear, 0xd5);
> }
> +#endif
>
> +#if CONFIG_PCM_MULAW_DECODER || CONFIG_PCM_MULAW_ENCODER
> static void pcm_ulaw_tableinit(void)
> {
> build_xlaw_table(linear_to_ulaw, ulaw2linear, 0xff);
> }
> +#endif
>
> +#if CONFIG_PCM_VIDC_DECODER || CONFIG_PCM_VIDC_ENCODER
> static void pcm_vidc_tableinit(void)
> {
> build_xlaw_table(linear_to_vidc, vidc2linear, 0xff);
> }
> +#endif
> #endif /* CONFIG_HARDCODED_TABLES */
This is static stuff; the compiler can already optimize it away when it
sees that it is not referenced by anything that is kept.
>
> #endif /* AVCODEC_PCM_TABLEGEN_H */
More information about the ffmpeg-devel
mailing list