[Libav-user] 答复: Decoding opus

He Lei helei0908 at hotmail.com
Wed Jan 11 17:42:44 EET 2017

Sorry, I only speak a little English;

You mean to say, the decoded frame->pkt_size is same as packet->size ?

But, the frame->pkt_size == packet->size,it is true; You need to look at annotation of AVFrame;

If you want get the Frame data size, that is frame->linesize[x];
if the decoded data of audio is plane, frame->data[n] is n th channel data of samples;
frame->nb_channels is num of channels;
frame->nb_samples is num of samples;

//can get all data length like this:
int iDataLen = 0;
for(int i=0; i< frame->nb_channels; ++i)
iDataLen +=frame->linesize[i];
uint8 * pData = frame->data[0];// it is continuous of all channel data;

may be a better way,but I do not know…..

if it is not plane, only frame->data[0], and frame->linesize[0] is the length;

发件人: Libav-user <libav-user-bounces at ffmpeg.org> 代表 Aboobeker Sidhik Koyamparambil mammu <aboosidhik at gmail.com>
发送时间: 2017年1月11日 14:27
收件人: This list is about using libavcodec, libavformat, libavutil, libavdevice and libavfilter.
主题: Re: [Libav-user] Decoding opus

No. I get the same data that I send to decoder. Not the uncompressed data (pcm) as output. In my case single frame in a single AV packet size. This I checked using a while loop that compares the packet size.


On 11 January 2017 at 14:23, He Lei <helei0908 at hotmail.com<mailto:helei0908 at hotmail.com>> wrote:
do you say ,you write same packet to decoder, and get frame more then in packet?
look at anntation as avcodec_decode_audio4();
that is:

4643  * Some decoders may support multiple frames in a single AVPacket. Such

4644  * decoders would then just decode the first frame and the return value would be

4645  * less than the packet size. In this case, avcodec_decode_audio4 has to be

4646  * called again with an AVPacket containing the remaining data in order to

4647  * decode the second frame, etc...  Even if no frames are returned, the packet

4648  * needs to be fed to the decoder with remaining data until it is completely

4649  * consumed or an error occurs.

4650  *

good luck
发自我的 iPhone

在 2017年1月11日,20:08,Aboobeker Sidhik Koyamparambil mammu <aboosidhik at gmail.com<mailto:aboosidhik at gmail.com>> 写道:

Dear All,

I am trying to decode opus. When I use both methods
avcodec_decode_audio4 and (avcodec_send_packet /avcodec_receive_frame) . I am receiving the same opus packet that I send for decoding. I got this by using the packet size of the decoded frame. Packet size is same as the input opus packet size.

I followed the decoding example given in github of ffmpeg. Please help me. Why I am receiving same packet as input?

AVCodec *codec;
AVCodecContext *c = NULL;
AVPacket avpkt;
AVFrame *decoded_frame = NULL;
codec = avcodec_find_decoder(AV_CODEC_ID_OPUS);
if (!codec) {
     printf("Codec not found\n");
c = avcodec_alloc_context3(codec);
if (!c) {
   printf("Could not allocate audio codec context\n");
/* put sample parameters */
c->sample_rate = 48000;
c->request_sample_fmt = AV_SAMPLE_FMT_FLT;
c->channels = 2;
/* open it */
if (avcodec_open2(c, codec, NULL) < 0) {
    printf("Could not open codec\n");

AVPacket avpkt;
AVFrame *decoded_frame = NULL;
avpkt.data = Buffer;  // Buffer is packet data here
avpkt.size = len;    // length of the packet
int i, ch;

if (!decoded_frame) {
    if (!(decoded_frame = av_frame_alloc())) {
        RELAY_SERVER_PRINT("Could not allocate audio frame\n");
int ret;
int got_frame = 0;
ret = avcodec_decode_audio4(client_sockt_num_1->c, decoded_frame, &got_frame, &avpkt);
if (ret < 0) {
        fprintf(stderr, "Error decoding audio frame (%s)\n", av_err2str(ret));
        return ret;
printf("length %i\n", decoded_frame->pkt_size);

Kind Regards

Aboobeker Sidhik
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Kind Regards

Aboobeker Sidhik
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