audio: ffmpeg_dec: add ALAC decoder and FLAC/ALAC encoder support by lgirdwood · Pull Request #11427 · thesofproject/sof

lgirdwood · 2026-11-09T21:49:20Z

Add Phase 1 lossless compress playback and capture codecs to ffmpeg_dec using native fixed-point libavcodec implementations:

ALAC decoder (CONFIG_FFMPEG_DEC_ALAC, SND_AUDIOCODEC_ALAC):
- Apple .caf container parser (kuki chunk 36-byte ALAC magic cookie extraction and data chunk framing) and inline 36-byte QuickTime 'alac' atom header support.
- Self-delimiting unparsed frame consumption tracking via GetBitContext and partial-frame reassembly across LL period boundaries.
FLAC encoder (CONFIG_FFMPEG_ENC_FLAC, SND_AUDIOCODEC_FLAC):
- Native libavcodec flac encoder configured with fixed integer LPC predictors (FF_LPC_TYPE_FIXED, compression_level = 1) for deterministic low-MCPS DSP encoding.
- Prepends the 42-byte "fLaC" + STREAMINFO metadata block from avctx->extradata to produce a self-contained .flac stream.
- Bounds FlacEncodeContext dimensions on a build-tree copy of flacenc.c (FLAC_MAX_BLOCKSIZE=1152, rc_sums[1], FLAC_MAX_CHANNELS=2), reducing context allocation 122x from 7.35 MiB to 43.5 KiB.
ALAC encoder (CONFIG_FFMPEG_ENC_ALAC, SND_AUDIOCODEC_ALAC):
- Native libavcodec alac encoder configured with fixed LPC prediction (compression_level = 1) and planar S16 input conversion.
- Prepends the 36-byte QuickTime 'alac' magic cookie from avctx->extradata.
Topologies & Base FW Capabilities:
- Advertise SND_AUDIOCODEC_ALAC playback and SND_AUDIOCODEC_FLAC / SND_AUDIOCODEC_ALAC capture in IPC4_SOF_CODEC_INFO.
- Add sof-hda-generic-ffmpeg-alac-compr, sof-hda-generic-ffmpeg-flac-enc-compr, and sof-hda-generic-ffmpeg-alac-enc-compr development topology targets.

Hardware Verification (Aphid PTL ACE 3.0 & Spider TGL CAVS 2.5)

Verified end-to-end on both Aphid (ptl) and Spider (tgl):

ALAC .caf playback (comprC0D50, codec_id=15)
FLAC capture encode (comprC0D51, codec_id=10) + round-trip playback (comprC0D50)
ALAC capture encode (comprC0D51, codec_id=15) + round-trip playback (comprC0D50)

Advertise SND_AUDIOCODEC_ALAC decode and SND_AUDIOCODEC_FLAC / SND_AUDIOCODEC_ALAC encode capabilities in base_fw when the corresponding FFmpeg Kconfig options are enabled. Signed-off-by: Liam Girdwood <liam.r.girdwood@linux.intel.com>

Extend the FFmpeg decode and encode adapter infrastructure to support container-framed and variable-blocksize lossless codecs: - Add frame_bytes_consumed hook and unparsed packet reassembly buffer handling in ffmpeg_dec-ffmpeg.c for codecs without a standalone AVCodecParser (such as ALAC). - Extend ffmpeg_dec_pcm_to_frame() in ffmpeg_dec-convert.c to support AV_SAMPLE_FMT_S16, AV_SAMPLE_FMT_S16P, AV_SAMPLE_FMT_S32, and AV_SAMPLE_FMT_S32P sample formats. - Add an optional encoder flush() hook in struct ffmpeg_enc_codec_ops and support native libavcodec encoders in ffmpeg.cmake. Signed-off-by: Liam Girdwood <liam.r.girdwood@linux.intel.com>

Add Apple Lossless Audio Codec (ALAC, SND_AUDIOCODEC_ALAC) decoder support via libavcodec's integer alac decoder: - Support raw ALAC packets with 36-byte out-of-band magic cookie extradata as well as self-contained Core Audio Format (.caf) streams. - Resize the PCM output staging buffer if the magic cookie's max_samples per frame exceeds the initial allocation. Signed-off-by: Liam Girdwood <liam.r.girdwood@linux.intel.com>

Add native libavcodec FLAC lossless encoder (SND_AUDIOCODEC_FLAC) support for compress capture streams: - Use fixed integer LPC predictors (FF_LPC_TYPE_FIXED, compression_level 1) with 1152-sample blocks and zero floating-point instructions in the per-frame encode path. - Prepend the 42-byte "fLaC" + STREAMINFO header on stream start and convert input PCM via ffmpeg_dec_pcm_to_frame(). Signed-off-by: Liam Girdwood <liam.r.girdwood@linux.intel.com>

Add native libavcodec ALAC lossless encoder (SND_AUDIOCODEC_ALAC) support for 1..2 channel compress capture streams: - Configure 1024-sample frame size using pure integer prediction and adaptive Rice coding. - Prepend a 64-byte Core Audio Format (.caf) header ("caff" + "desc" + "kuki" + "data") so captured streams are directly decodable. Signed-off-by: Liam Girdwood <liam.r.girdwood@linux.intel.com>

Add development topology targets for ALAC compress playback and FLAC/ALAC compress capture on CAVS 2.5 and ACE 3.0. Signed-off-by: Liam Girdwood <liam.r.girdwood@linux.intel.com>

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9 open issues

The sed rule s/FLAC_MAX_BLOCKSIZE/1152/g replaces the macro name everywhere, which can break… · New
cd->in_buf is used for header sniffing (memcmp / alac_read_be32) without first… · New
When prev_len == 0, the code passes in directly to libavcodec (pkt_data = in) without… · New
ffmpeg_dec_pcm_to_frame() return value is ignored here as well. Please handle conversion failures… · New
ffmpeg_dec_pcm_to_frame() returns an error code, but the result is ignored. If it fails (e.g.,… · New
This relies on the internal layout of libavcodec's private ALACContext (priv_data) to read… · New
This relies on the internal layout of libavcodec's private ALACContext (priv_data) to read… · New
av_log_set_level() changes a global libav* logging level, which can affect other decoder/encoder… · New
These comments say encode is provided via ffmpeg_dec, but the encode path is implemented under… · New

_{Review effort: Lite}

+if(CONFIG_FFMPEG_ENC_FLAC)
+	set(_ff_extra_cflags "${_ff_extra_cflags} -I${SOF_FFMPEG_SRC_DIR}/libavcodec")
+	set(_ff_flacenc_prep
+		COMMAND sh -c "sed -e 's/FLAC_MAX_BLOCKSIZE/1152/g' -e 's/rc_sums\\[32\\]/rc_sums[1]/g' -e 's/subframes\\[FLAC_MAX_CHANNELS\\]/subframes[2]/g' -e 's/channels > FLAC_MAX_CHANNELS/channels > 2/g' <SOURCE_DIR>/libavcodec/flacenc.c > <BINARY_DIR>/libavcodec/flacenc.c")


+	avail = source_get_data_available(src);
+
+	/* Step 4: Check for the 8-byte Core Audio Format ("caff\x00\x01\x00\x00") header */
+	if (memcmp(cd->in_buf, "caff", 4) == 0) {
+		if (avail < 8)
+			return -ENODATA;
+
+		comp_info(dev, "CAF header detected, parsing ALAC container chunks");
+		source_drop_data(src, 8);
+		cd->alac_parsing_caf = true;
+		return ffmpeg_dec_alac_skip_container(mod, src);
+	}
+
+	/* Step 5: Check for an inline 36-byte QuickTime 'alac' atom prefix */
+	if (avail >= 8 &&
+	    alac_read_be32(cd->in_buf) == ALAC_EXTRADATA_SIZE &&
+	    memcmp(&cd->in_buf[4], "alac", 4) == 0) {
+		if (avail < ALAC_EXTRADATA_SIZE)
+			return -ENODATA;


+		} else if (prev_len == 0) {
+			pkt_data = in;
+			pkt_len = in_size;
+		} else {
+			size_t space = prev_len < cap ? cap - prev_len : 0;
+			size_t copy = in_size < space ? in_size : space;
+
+			if (copy) {
+				memcpy_s(ff->pktbuf + prev_len, space, in, copy);
+				memset(ff->pktbuf + prev_len + copy, 0,
+				       AV_INPUT_BUFFER_PADDING_SIZE);
+			}
+			pkt_data = ff->pktbuf;
+			pkt_len = prev_len + copy;
+		}


+	ffmpeg_dec_pcm_to_frame(e->pcm_in, alac->frame,
+				e->src_fmt, ch, e->nb);


+	ffmpeg_dec_pcm_to_frame(e->pcm_in, flac->frame,
+				e->src_fmt, ch, e->nb);


+struct alac_priv_prefix {
+	const void *av_class;
+	void *avctx;
+	const uint8_t *gb_buffer;
+	const uint8_t *gb_buffer_end;
+	int gb_index;
+};


+static size_t ffmpeg_dec_alac_frame_bytes_consumed(const void *priv_data)
+{
+	const struct alac_priv_prefix *priv = priv_data;
+
+	if (!priv || priv->gb_index <= 0)
+		return 0;
+
+	return (size_t)((priv->gb_index + 7) >> 3);
+}


+		av_log_set_level(AV_LOG_FATAL);
+		ret = avcodec_send_packet(ff->avctx, ff->pkt);
+		if (ret == 0)
+			ret = avcodec_receive_frame(ff->avctx, ff->frame);
+		av_log_set_level(AV_LOG_ERROR);


+#if defined(CONFIG_FFMPEG_ENC_FLAC)
+	/* FLAC encode (compress capture) via ffmpeg_dec (native libavcodec). */
+	codec_info.items[codec_info.count++] =
+		SET_CODEC_INFO_ITEM(SND_AUDIOCODEC_FLAC, SOF_IPC_STREAM_CAPTURE);
+#endif
+#if defined(CONFIG_FFMPEG_ENC_ALAC)
+	/* ALAC encode (compress capture) via ffmpeg_dec (native libavcodec). */
+	codec_info.items[codec_info.count++] =
+		SET_CODEC_INFO_ITEM(SND_AUDIOCODEC_ALAC, SOF_IPC_STREAM_CAPTURE);
+#endif


lgirdwood mentioned this pull request Nov 10, 2026

ffmpeg_dec: add Bluetooth SBC/mSBC, G.722, and aptX decode and encode support #11431

Merged

lgirdwood force-pushed the topic/ffmpeg-lossless branch from f41fccf to 2a735e9 Compare November 10, 2026 11:51

lrgirdwo added 5 commits November 11, 2026 00:00

topology2: add ALAC decode and FLAC/ALAC encode topologies

e3da217

Add development topology targets for ALAC compress playback and FLAC/ALAC compress capture on CAVS 2.5 and ACE 3.0. Signed-off-by: Liam Girdwood <liam.r.girdwood@linux.intel.com>

lgirdwood force-pushed the topic/ffmpeg-lossless branch from 2a735e9 to e3da217 Compare November 11, 2026 00:00

lgirdwood requested a balanced review from Copilot November 11, 2026 20:27

Copilot AI reviewed Nov 11, 2026

lgirdwood requested a balanced review from Copilot November 13, 2026 17:41

Copilot AI reviewed Nov 13, 2026

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audio: ffmpeg_dec: add ALAC decoder and FLAC/ALAC encoder support - #11427

audio: ffmpeg_dec: add ALAC decoder and FLAC/ALAC encoder support#11427
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		ffmpeg_dec_pcm_to_frame(e->pcm_in, alac->frame,
		e->src_fmt, ch, e->nb);

		ffmpeg_dec_pcm_to_frame(e->pcm_in, flac->frame,
		e->src_fmt, ch, e->nb);

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lgirdwood commented Nov 9, 2026

Hardware Verification (Aphid PTL ACE 3.0 & Spider TGL CAVS 2.5)

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