Re: [FFmpeg-devel] [PATCH v2 2/5] avdevice/alsa_dec: make sure we have enough data in non-blocking mode

[Marton Balint]

On Mon, 1 Mar 2021, Marton Balint wrote:

Otherwise we might return 1-2 samples per packet if av_read_frame() call rate is
only sligthly less than the stream sample rate.

Ping for this and the rest of the series. Note that the approach in 
this patch makes 1/5 unneeded because constant frame size is now indeed 
guaranteed.

Regards,
Marton


Signed-off-by: Marton Balint <c...@passwd.hu>
---
libavdevice/alsa.c     |  5 +++++
libavdevice/alsa.h     |  1 +
libavdevice/alsa_dec.c | 22 ++++++++++++----------
3 files changed, 18 insertions(+), 10 deletions(-)

diff --git a/libavdevice/alsa.c b/libavdevice/alsa.c
index 117b2ea144..ee282fac16 100644
--- a/libavdevice/alsa.c
+++ b/libavdevice/alsa.c
@@ -286,6 +286,10 @@ av_cold int ff_alsa_open(AVFormatContext *ctx, 
snd_pcm_stream_t mode,
        }
    }

+    s->pkt = av_packet_alloc();
+    if (!s->pkt)
+        goto fail1;
+
    s->h = h;
    return 0;

@@ -308,6 +312,7 @@ av_cold int ff_alsa_close(AVFormatContext *s1)
    if (CONFIG_ALSA_INDEV)
        ff_timefilter_destroy(s->timefilter);
    snd_pcm_close(s->h);
+    av_packet_free(&s->pkt);
    return 0;
}

diff --git a/libavdevice/alsa.h b/libavdevice/alsa.h
index 1ed8c82199..07783c983a 100644
--- a/libavdevice/alsa.h
+++ b/libavdevice/alsa.h
@@ -58,6 +58,7 @@ typedef struct AlsaData {
    void *reorder_buf;
    int reorder_buf_size; ///< in frames
    int64_t timestamp; ///< current timestamp, without latency applied.
+    AVPacket *pkt;
} AlsaData;

/**
diff --git a/libavdevice/alsa_dec.c b/libavdevice/alsa_dec.c
index 6d568737b3..88bf32d25f 100644
--- a/libavdevice/alsa_dec.c
+++ b/libavdevice/alsa_dec.c
@@ -104,34 +104,36 @@ static int audio_read_packet(AVFormatContext *s1, 
AVPacket *pkt)
    int64_t dts;
    snd_pcm_sframes_t delay = 0;

-    if (av_new_packet(pkt, s->period_size * s->frame_size) < 0) {
-        return AVERROR(EIO);
+    if (!s->pkt->data) {
+        int ret = av_new_packet(s->pkt, s->period_size * s->frame_size);
+        if (ret < 0)
+            return ret;
+        s->pkt->size = 0;
    }

-    while ((res = snd_pcm_readi(s->h, pkt->data, s->period_size)) < 0) {
+    do {
+        while ((res = snd_pcm_readi(s->h, s->pkt->data + s->pkt->size, s->period_size - 
s->pkt->size / s->frame_size)) < 0) {
        if (res == -EAGAIN) {
-            av_packet_unref(pkt);
-
            return AVERROR(EAGAIN);
        }
+        s->pkt->size = 0;
        if (ff_alsa_xrun_recover(s1, res) < 0) {
            av_log(s1, AV_LOG_ERROR, "ALSA read error: %s\n",
                   snd_strerror(res));
-            av_packet_unref(pkt);
-
            return AVERROR(EIO);
        }
        ff_timefilter_reset(s->timefilter);
-    }
+        }
+        s->pkt->size += res * s->frame_size;
+    } while (s->pkt->size < s->period_size * s->frame_size);

+    av_packet_move_ref(pkt, s->pkt);
    dts = av_gettime();
    snd_pcm_delay(s->h, &delay);
    dts -= av_rescale(delay + res, 1000000, s->sample_rate);
    pkt->pts = ff_timefilter_update(s->timefilter, dts, s->last_period);
    s->last_period = res;

-    pkt->size = res * s->frame_size;
-
    return 0;
}

--
2.26.2

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