avformat/daudenc: force 2000 sample packet size with a bsf

The samples I found all have 2000 sample packets, and by forcing the packet
size with a bsf we could automagically make muxing work for packets containing
more than 3640 samples.
Signed-off-by: Marton Balint <cus@passwd.hu>

configure

@@ -3518,6 +3518,7 @@ caf_demuxer_select="iso_media"
 caf_muxer_select="iso_media"
 dash_muxer_select="mp4_muxer"
 dash_demuxer_deps="libxml2"
+daud_muxer_select="pcm_rechunk_bsf"
 dirac_demuxer_select="dirac_parser"
 dts_demuxer_select="dca_parser"
 dtshd_demuxer_select="dca_parser"

doc/muxers.texi

@@ -1397,23 +1397,17 @@ D-Cinema audio muxer.
 It accepts a single 6-channels audio stream resampled at 96000 Hz
 encoded with the @samp{pcm_24daud} codec.
 
-In addition, each muxed packet size must not be greater than 65535 bytes.
-
 @subsection Example
 Use @command{ffmpeg} to mux input audio to a @samp{5.1} channel layout
 resampled at 96000Hz:
 @example
-ffmpeg -i INPUT -af aresample=96000,pan=5.1,asetnsamples=3640 slow.302
-@end example
-
-The @samp{asetnsamples} filter is used to reduce the number of samples
-of each audio packet, with a size computed according to the formula:
-@example
-65535 / (@var{channels} * @var{encoded_sample_size}) = 655535 / (6 * 3) = 3640
+ffmpeg -i INPUT -af aresample=96000,pan=5.1 slow.302
 @end example
 
-The @var{encoded_sample_size} = 3 factor is due to sample size of the
-@samp{pcm_24daud} encoder.
+For ffmpeg versions before 7.0 you might have to use the @samp{asetnsamples}
+filter to limit the muxed packet size, because this format does not support
+muxing packets larger than 65535 bytes (3640 samples). For newer ffmpeg
+versions audio is automatically packetized to 36000 byte (2000 sample) packets.
 
 @section dv
 DV (Digital Video) muxer.

libavformat/daudenc.c

@@ -25,6 +25,7 @@
 static int daud_init(struct AVFormatContext *s)
 {
     AVCodecParameters *par = s->streams[0]->codecpar;
+    int ret;
 
     if (par->ch_layout.nb_channels != 6) {
         av_log(s, AV_LOG_ERROR,
@@ -40,17 +41,15 @@ static int daud_init(struct AVFormatContext *s)
         return AVERROR(EINVAL);
     }
 
+    ret = ff_stream_add_bitstream_filter(s->streams[0], "pcm_rechunk", "n=2000:pad=0");
+    if (ret < 0)
+        return ret;
+
     return 0;
 }
 
 static int daud_write_packet(struct AVFormatContext *s, AVPacket *pkt)
 {
-    if (pkt->size > 65535) {
-        av_log(s, AV_LOG_ERROR,
-               "Packet size %d too large for s302m, must be <= 65535.\n",
-               pkt->size);
-        return AVERROR_INVALIDDATA;
-    }
     avio_wb16(s->pb, pkt->size);
     avio_wb16(s->pb, 0x8010); // unknown
     avio_write(s->pb, pkt->data, pkt->size);

tests/ref/fate/dcinema-encode

@@ -7,23 +7,14 @@
 #sample_rate 0: 96000
 #channel_layout_name 0: 5.1(side)
 #stream#, dts,        pts, duration,     size, hash
-0,          0,          0,     1024,    12288, 848250bf0a20e324f60151629134ebd5
-0,       1024,       1024,     1024,    12288, cd3c42240d163a7e8835aeda9538f881
-0,       2048,       2048,     1024,    12288, f213a268e7ab62b53a4a4acb9b303dfb
-0,       3072,       3072,     1024,    12288, 14d4f3289b057394abc995bfea58912a
-0,       4096,       4096,     1024,    12288, a69453c3f0c23abfacb49b15aedc432a
-0,       5120,       5120,     1024,    12288, 6578b4a89b1fa4c8897b1376974b685d
-0,       6144,       6144,     1024,    12288, 4893b62addf1bea4c03c173f173aa082
-0,       7168,       7168,     1024,    12288, 992b70ea94c339dfda2d3514ac56c4a9
-0,       8192,       8192,     1024,    12288, 543f85139b77d30f8a46fd22d63e3ec7
-0,       9216,       9216,     1024,    12288, f52f825a2fe71f66786d5cd08487e271
-0,      10240,      10240,     1024,    12288, 50ac352cd73a803f52bfd393e610f83b
-0,      11264,      11264,     1024,    12288, e9475a9a8794b9b0b912b855bc05001f
-0,      12288,      12288,     1024,    12288, bf205474f44a381583b1f077ab8a9d0c
-0,      13312,      13312,     1024,    12288, f5655b1da90d808c7e05b4bda02233ca
-0,      14336,      14336,     1024,    12288, f8493bb74a270b50706cace85549c317
-0,      15360,      15360,     1024,    12288, c299fbbdcae68c97bca63210f6a1f7da
-0,      16384,      16384,     1024,    12288, 2f263932e3d4c419853e3369d70ef8d9
-0,      17408,      17408,     1024,    12288, 09862736b8a1a1ce5c8d23814fb054cd
-0,      18432,      18432,     1024,    12288, a99506638c5a3d84d3fa46ee2ba6c5ad
-0,      19456,      19456,     1024,    12288, ab6f04f68cfbf2c9a89e9641604b3a50
+0,          0,          0,     2000,    24000, f7b7be0b72225eeaa98ec0b2ea7ad34d
+0,       2000,       2000,     2000,    24000, c2d1d19b65f9ec1f7415bce5f2fbac8e
+0,       4000,       4000,     2000,    24000, 461979d3566bc69cd4d1911ed1559191
+0,       6000,       6000,     2000,    24000, 8fe028dc7a9e5512b6c24d33cf76c4f6
+0,       8000,       8000,     2000,    24000, 8f7be8b0e562cc56110ee5de6b97bec3
+0,      10000,      10000,     2000,    24000, 53f053a72010471bd1a150af0873ec4a
+0,      12000,      12000,     2000,    24000, adcfe7407ec384f65f384cfd85793963
+0,      14000,      14000,     2000,    24000, 4c541973df0e37a77eca16022d4d316c
+0,      16000,      16000,     2000,    24000, 362d410570c821384e3ba30a03cdc907
+0,      18000,      18000,     2000,    24000, 00643563149102a4834841217a85d284
+0,      20000,      20000,      480,     5760, 7401d92e7105169bef3deb34e53e9605