High bitrate compressed audio data like DTS HD or MAT is usually packed into 8-channel data. The HDMI specs state this has to be formatted as a single IEC958 stream, compared to normal multi- channel PCM data which has to be formatted as parallel IEC958 streams.

As this single-stream formatting mode may break existing setups that expect non-PCM multichannel data to be formatted as parallel IEC958 streams it needs to be explicitly selected by setting the hdmi_mode option to true.

The single-stream formatting implementation is prepared to cope with arbitrary channel counts but only limited testing was done for channel counts other than 8.

Signed-off-by: Matthias Reichl hias@horus.com --- src/pcm/pcm_iec958.c | 37 +++++++++++++++++++++++++++++++++---- 1 file changed, 33 insertions(+), 4 deletions(-)

diff --git a/src/pcm/pcm_iec958.c b/src/pcm/pcm_iec958.c index 76d3ca7b..17ade957 100644 --- a/src/pcm/pcm_iec958.c +++ b/src/pcm/pcm_iec958.c @@ -63,6 +63,7 @@ struct snd_pcm_iec958 { unsigned int byteswap; unsigned char preamble[3]; /* B/M/W or Z/X/Y */ snd_pcm_fast_ops_t fops; + int hdmi_mode; };

enum { PREAMBLE_Z, PREAMBLE_X, PREAMBLE_Y }; @@ -193,6 +194,10 @@ static void snd_pcm_iec958_encode(snd_pcm_iec958_t *iec, unsigned int channel; int32_t sample = 0; int counter = iec->counter; + int single_stream = iec->hdmi_mode && + (iec->status[0] & IEC958_AES0_NONAUDIO) && + (channels == 8); + int counter_step = single_stream ? ((channels + 1) >> 1) : 1; for (channel = 0; channel < channels; ++channel) { const char *src; uint32_t *dst; @@ -205,7 +210,12 @@ static void snd_pcm_iec958_encode(snd_pcm_iec958_t *iec, src_step = snd_pcm_channel_area_step(src_area); dst_step = snd_pcm_channel_area_step(dst_area) / sizeof(uint32_t); frames1 = frames; - iec->counter = counter; + + if (single_stream) + iec->counter = (counter + (channel >> 1)) % 192; + else + iec->counter = counter; + while (frames1-- > 0) { goto *get; #define GET32_END after @@ -217,9 +227,11 @@ static void snd_pcm_iec958_encode(snd_pcm_iec958_t *iec, *dst = sample; src += src_step; dst += dst_step; - iec->counter++; + iec->counter += counter_step; iec->counter %= 192; } + if (single_stream) /* set counter to ch0 value for next iteration */ + iec->counter = (counter + frames * counter_step) % 192; } } #endif /* DOC_HIDDEN */ @@ -473,6 +485,7 @@ static const snd_pcm_ops_t snd_pcm_iec958_ops = { * \param close_slave When set, the slave PCM handle is closed with copy PCM * \param status_bits The IEC958 status bits * \param preamble_vals The preamble byte values + * \param hdmi_mode When set, enable HDMI compliant formatting * \retval zero on success otherwise a negative error code * \warning Using of this function might be dangerous in the sense * of compatibility reasons. The prototype might be freely @@ -481,7 +494,8 @@ static const snd_pcm_ops_t snd_pcm_iec958_ops = { int snd_pcm_iec958_open(snd_pcm_t **pcmp, const char *name, snd_pcm_format_t sformat, snd_pcm_t *slave, int close_slave, const unsigned char *status_bits, - const unsigned char *preamble_vals) + const unsigned char *preamble_vals, + int hdmi_mode) { snd_pcm_t *pcm; snd_pcm_iec958_t *iec; @@ -519,6 +533,8 @@ int snd_pcm_iec958_open(snd_pcm_t **pcmp, const char *name, snd_pcm_format_t sfo

memcpy(iec->preamble, preamble_vals, 3);

+ iec->hdmi_mode = hdmi_mode; + err = snd_pcm_new(&pcm, SND_PCM_TYPE_IEC958, name, slave->stream, slave->mode); if (err < 0) { free(iec); @@ -566,9 +582,14 @@ pcm.name { [preamble.z or preamble.b val] [preamble.x or preamble.m val] [preamble.y or preamble.w val] + [hdmi_mode true] } \endcode

+When <code>hdmi_mode</code> is true, 8-channel compressed data is +formatted as 4 contiguous frames of a single IEC958 stream as required +by the HDMI HBR specification. + \subsection pcm_plugins_iec958_funcref Function reference

<UL> @@ -605,6 +626,7 @@ int _snd_pcm_iec958_open(snd_pcm_t **pcmp, const char *name, unsigned char preamble_vals[3] = { 0x08, 0x02, 0x04 /* Z, X, Y */ }; + int hdmi_mode = 0;

snd_config_for_each(i, next, conf) { snd_config_t *n = snd_config_iterator_entry(i); @@ -633,6 +655,13 @@ int _snd_pcm_iec958_open(snd_pcm_t **pcmp, const char *name, preamble = n; continue; } + if (strcmp(id, "hdmi_mode") == 0) { + err = snd_config_get_bool(n); + if (err < 0) + continue; + hdmi_mode = err; + continue; + } SNDERR("Unknown field %s", id); return -EINVAL; } @@ -707,7 +736,7 @@ int _snd_pcm_iec958_open(snd_pcm_t **pcmp, const char *name, return err; err = snd_pcm_iec958_open(pcmp, name, sformat, spcm, 1, status ? status_bits : NULL, - preamble_vals); + preamble_vals, hdmi_mode); if (err < 0) snd_pcm_close(spcm); return err;