STRUCT SND_COMPR_TSTAMP(9)

💖 struct snd_compr_tstamp(9) — bestie's guide 💖

okay so welcome to the kernel API manual, specifically the page for struct snd_compr_tstamp, and yes it's in section 9, and yes we're gonna get into it 🎀

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✨ NAME ✨

struct snd_compr_tstamp — the timestamp descriptor. that's it, that's the whole vibe. it's the little struct that keeps track of when and how much stuff is moving through your compressed audio stream 🦋

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🌸 SYNOPSIS 🌸

here's the whole thing, no cap, exactly how it looks:

struct snd_compr_tstamp {
    __u32 byte_offset;
    __u32 copied_total;
    __u32 pcm_frames;
    __u32 pcm_io_frames;
    __u32 sampling_rate;
 };

five __u32 fields, all lined up like a little squad 💅

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👑 Members 👑

okay this is the part where we meet each field individually. group chat introductions, let's go 🫶

• byte_offset — the byte offset in the ring buffer, pointing at the DSP. like, where in the buffer is the DSP actually at rn 📍
• copied_total — the total number of bytes copied from the ring buffer to the DSP, or to the ring buffer by the DSP. total. cumulative. the whole count 💯
• pcm_frames — frames decoded or encoded by the DSP. important bestie moment: this field will evolve by large steps and should only be used to monitor encoding/decoding progress. it shall not be used for timing estimates. like. don't do it. it's not that girl for timing 😭
• pcm_io_frames — frames rendered or received by the DSP into a mixer or an audio output/input. this is the field you want for A/V sync or time estimates. this one ate and left no crumbs 🔥
• sampling_rate — the sampling rate of the audio. sample rate. of the audio. that's the whole thing 🎵

quick recap so nobody mixes them up: pcm_frames = progress monitor only (big steps, no timing), pcm_io_frames = the actual timing/sync icon. iykyk ⭐

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🌈 SEE ALSO 🌈

go read these next, they're all in the kernel file ./include/uapi/sound/compress_offload.h and honestly it's giving family reunion:

• struct snd_compressed_buffer(9)
• struct snd_compr_params(9)
• struct snd_compr_tstamp64(9)
• struct snd_compr_avail(9)
• struct snd_compr_avail64(9)
• struct snd_compr_caps(9)
• struct snd_compr_codec_caps(9)
• enum sndrv_compress_encoder(9)
• struct snd_compr_metadata(9)
• struct snd_compr_task(9)
• enum snd_compr_state(9)
• struct snd_compr_task_status(9)

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💀 reminder: pcm_frames is for progress-monitoring only. timing estimates from it = undefined behaviour in spirit. use pcm_io_frames and thank me later 🙈

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and that's the page!! this one lives at ./include/uapi/sound, dated October 2026, and it's filed under struct snd_compr_tstamp(9) in section 9 of the Kernel API Manual — mwah, drink water, go sync your A/V properly 🧚💜💅