[vlc-devel] [PATCH 2/2] audio_output: coreaudio: use int64_t for host time
Thomas Guillem
thomas at gllm.fr
Thu Jul 23 10:31:19 CEST 2020
cf. https://developer.apple.com/documentation/coreaudiotypes/audiotimestamp/1422266-mhosttime
Host time is an uint64_t.
Should we instead fix the unsigned calculation?
It seems that on iOS, the host_time can be before mach_absolute_time() ? We should debug why it happens. It the host_time always late or only the first ones?
On Thu, Jul 23, 2020, at 09:57, Alexandre Janniaux wrote:
> The computation was leading to very high render_delay (for example in
> some measurement, render_delay = 6148914691236500), and so glitch during
> playback with for instance the following warnings:
>
> libvlc video output warning: picture is too late to be displayed
> (missing 4279998112535367 ms)
>
> Instead, use int64_t for host_time. Unsignedness is kept for computation
> on frames / bytes.
> ---
> modules/audio_output/coreaudio_common.c | 23 +++++++++++++----------
> modules/audio_output/coreaudio_common.h | 6 +++---
> 2 files changed, 16 insertions(+), 13 deletions(-)
>
> diff --git a/modules/audio_output/coreaudio_common.c
> b/modules/audio_output/coreaudio_common.c
> index 797c3e623d..b3df6289b8 100644
> --- a/modules/audio_output/coreaudio_common.c
> +++ b/modules/audio_output/coreaudio_common.c
> @@ -46,16 +46,17 @@ FramesToBytes(struct aout_sys_common *p_sys,
> uint64_t i_frames)
> static inline uint64_t
> UsToFrames(struct aout_sys_common *p_sys, vlc_tick_t i_us)
> {
> + assert(i_us > 0);
> return samples_from_vlc_tick(i_us, p_sys->i_rate);
> }
>
> static inline vlc_tick_t
> -HostTimeToTick(struct aout_sys_common *p_sys, uint64_t i_host_time)
> +HostTimeToTick(struct aout_sys_common *p_sys, int64_t i_host_time)
> {
> return VLC_TICK_FROM_NS(i_host_time * p_sys->tinfo.numer /
> p_sys->tinfo.denom);
> }
>
> -static inline uint64_t
> +static inline int64_t
> TickToHostTime(struct aout_sys_common *p_sys, vlc_tick_t i_us)
> {
> return NS_FROM_VLC_TICK(i_us * p_sys->tinfo.denom / p_sys->tinfo.numer);
> @@ -124,7 +125,7 @@ ca_Open(audio_output_t *p_aout)
>
> /* Called from render callbacks. No lock, wait, and IO here */
> void
> -ca_Render(audio_output_t *p_aout, uint32_t i_frames, uint64_t
> i_host_time,
> +ca_Render(audio_output_t *p_aout, uint32_t i_frames, int64_t
> i_host_time,
> uint8_t *p_output, size_t i_requested)
> {
> struct aout_sys_common *p_sys = (struct aout_sys_common *)
> p_aout->sys;
> @@ -157,7 +158,7 @@ ca_Render(audio_output_t *p_aout, uint32_t
> i_frames, uint64_t i_host_time,
> * */
> const size_t i_requested_us =
> FramesToUs(p_sys, BytesToFrames(p_sys, i_requested));
> - const uint64_t i_requested_host_time =
> + const int64_t i_requested_host_time =
> TickToHostTime(p_sys, i_requested_us);
> if (p_sys->i_first_render_host_time >= i_host_time +
> i_requested_host_time)
> {
> @@ -169,7 +170,7 @@ ca_Render(audio_output_t *p_aout, uint32_t
> i_frames, uint64_t i_host_time,
> const vlc_tick_t i_silence_us =
> HostTimeToTick(p_sys, p_sys->i_first_render_host_time -
> i_host_time);
>
> - const uint64_t i_silence_bytes =
> + const size_t i_silence_bytes =
> FramesToBytes(p_sys, UsToFrames(p_sys, i_silence_us));
> assert(i_silence_bytes <= i_requested);
> memset(p_output, 0, i_silence_bytes);
> @@ -244,17 +245,19 @@ ca_TimeGet(audio_output_t *p_aout, vlc_tick_t *delay)
>
> if (p_sys->i_render_host_time == 0 || p_sys->i_first_render_host_time == 0)
> {
> + msg_Info(p_aout, "aout - not yet started");
stray debug
> /* Not yet started (or reached the first_render host time) */
> lock_unlock(p_sys);
> return -1;
> }
>
> - uint64_t i_render_delay_host_time = p_sys->i_render_host_time
> - - mach_absolute_time();
> + int64_t i_render_delay_host_time = p_sys->i_render_host_time
> + - mach_absolute_time();
> const vlc_tick_t i_render_delay =
> HostTimeToTick(p_sys, i_render_delay_host_time);
>
> - *delay = ca_GetLatencyLocked(p_aout) + i_render_delay;
> + vlc_tick_t latency = ca_GetLatencyLocked(p_aout);
> + *delay = latency + i_render_delay;
> lock_unlock(p_sys);
> return 0;
> }
> @@ -511,8 +514,8 @@ RenderCallback(void *p_data,
> AudioUnitRenderActionFlags *ioActionFlags,
> VLC_UNUSED(inTimeStamp);
> VLC_UNUSED(inBusNumber);
>
> - uint64_t i_host_time = (inTimeStamp->mFlags & kAudioTimeStampHostTimeValid)
> - ? inTimeStamp->mHostTime : 0;
> + int64_t i_host_time = (inTimeStamp->mFlags & kAudioTimeStampHostTimeValid)
> + ? inTimeStamp->mHostTime : 0;
>
> ca_Render(p_data, inNumberFrames, i_host_time,
> ioData->mBuffers[0].mData,
> ioData->mBuffers[0].mDataByteSize);
> diff --git a/modules/audio_output/coreaudio_common.h
> b/modules/audio_output/coreaudio_common.h
> index 4bd6139493..c757cf0042 100644
> --- a/modules/audio_output/coreaudio_common.h
> +++ b/modules/audio_output/coreaudio_common.h
> @@ -60,8 +60,8 @@ struct aout_sys_common
> bool b_played;
> block_t *p_out_chain;
> block_t **pp_out_last;
> - uint64_t i_render_host_time;
> - uint64_t i_first_render_host_time;
> + int64_t i_render_host_time;
> + int64_t i_first_render_host_time;
> uint32_t i_render_frames;
>
> vlc_sem_t flush_sem;
> @@ -86,7 +86,7 @@ struct aout_sys_common
>
> int ca_Open(audio_output_t *p_aout);
>
> -void ca_Render(audio_output_t *p_aout, uint32_t i_nb_samples, uint64_t
> i_host_time,
> +void ca_Render(audio_output_t *p_aout, uint32_t i_nb_samples, int64_t
> i_host_time,
> uint8_t *p_output, size_t i_requested);
>
> int ca_TimeGet(audio_output_t *p_aout, vlc_tick_t *delay);
> --
> 2.27.0
>
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