AAC RTP packets with multiple AU units per packet #81
Description
Thx for your continued effort to improve this asset...
I was wondering how you tested the AACPayload, but at least for me it does not work with e.g. ffmpeg.
Line 112 in 3ce0caf
Overall the code only works if there is just one AU unit present, as the AU units are usually lined up sequentially at the beginning of the payload and the header length (in byte / 2) gives the number of AUs present. The code assumes there is one AU unit, but as there are usually more, it might loose 2-3 other AU units and the outcome is choppy...
instead of using the while loop, I use this one, which seems to work fine:
int ptr = 0;
if (ptr + 2 > rtp_payload.Length) return audio_data; // 2 bytes for AU Header Length
// Get Size of the AU Header
int au_headers_length_bits = (((rtp_payload[ptr] << 8) + (rtp_payload[ptr + 1] << 0))); // 16 bits
int au_headers_length = (int)Math.Ceiling((double)au_headers_length_bits / 8.0);
ptr += 2;
int cnt = 0;
for(int p = 0; p < au_headers_length>>1; p++)
{
int aac_frame_size = (((rtp_payload[ptr + 2 * p] << 8) + (rtp_payload[ptr + 2 * p + 1] << 0)) >> 3); // 13 bits
int aac_index_delta = rtp_payload[ptr + 2 * p + 1] & 0x03; // 3 bits
// extract the AAC block
if ((ptr + au_headers_length + cnt ) + aac_frame_size > rtp_payload.Length) break; // not enough data to copy
byte[] aac_data = new byte[aac_frame_size];
Array.Copy(rtp_payload, (ptr + au_headers_length + cnt), aac_data, 0, aac_frame_size);
audio_data.Add(aac_data);
cnt += aac_frame_size;
}
return audio_data;
Any feedback would be great... cheers...